I do not know what your budget is so I am going to start small.

Get your self a modeling programme that you enjoy working with. If you do not like the interface of one or how it works then move on to another. There are some 3D Modelers listed on the wiki. MED imports .fbx and .x for nonanimated and animated models. It imports .obj and .3ds as well for static models. So make certain that the modeler you choose can export any one of those formats. OR that your modeler can export to 3d GameStudio .mdl format.

Milkshape is very inexpensive and exports directly to .mdl7 format. Milkshape Video Tutorials Free These are very well done and you will learn Milkshape modeling in no time.

Here are some resources. Use as many outside resources as possible to cut down on your workload so you can concentrate on the features that are unique to your game. Apples are apples Literally. So do not recreate an apple model if you find one that looks good to you. Most furniture can be used from outside sources but if you want a special throne for your villian then spend your time designing that with the look you want to give it.

Watch your scripts and make sure they say .c then they will be Lite-C. .wdl is C-Script.

Player movement
Dracula's walk script in Lite-C If you purchase IntenseX AI listed below it may already have a movement script.

Terrain
Mysty Moods by Loopix This will give you some awesome outdoor levels. He is excellent at making plants. He has some free plants but if you can afford it support him and purchase some from his site. I purchased his plant packs and am very happy with them.
Vegetation Template OR you can purchase Seed It

AI and scripting
IntenseX AI I talked with them about rpg elements and they are going to come out with a rpg one. So start with the copper version and keep up with the updates. You may not even have to do a lot of scripting if you get this. HOWEVER I would get familiar with Lite-C so you can do some custom scripts if need be. I have hired programmers but I am still going to mess around with Lite-C and try some things on my own just to learn it and become familiar with it.

Textures
CG Textures You can download 15mb per day for free. So bookmark this site and start downloading. Be failthful in downloading textures every day and you will have a nice library. I subscribe to this site and it is excellent. If you can afford to then pay for a subscription as to support this gentleman but if not he is very generous in letting non subscribers have free downloads.

Models and Textures
Terminal 26 They have free models and textures and terrain on this site that you can download. Their model packs are inexpensive so you can purchase those. Some models you will have to retexture but at least they are mapped already for you.
GameBeep
Rincewind's Medieval Houses Rincewind did an excellent job on these. Do not forget to grab the human model character Pappenheimer did on page 3. Do not forget to keep tabs on what you are using so you can include these people in your credits.
Medieval Weaponry Inexpensive

Main Menu Template This is .wdl which means C-Script. Hang on to it and you can convert the script to Lite-C later. It will be practise for you to get familiar with Lite-C and how it works. OR you can go through User Contributions or Lite-C User Contributions to find one you will not have to convert.

Human Characters and creatures
Fragmotion for animations.
My advise is to learn how to make nonanimated models first. The Milkshape videos or other tutorials depending on which modeler you choose will help you learn modeling. Then learn how to animate something simple like a book opening or a chest lid that opens. You can also purchase human character models that are not animated and animate them yourself or use bvh motions. TrueBones has bvh motions and will send you a few free that way you can see if you want to use those or not.

RPG Elements
Both of these are in Lite-C.
Inventory Morrowind style
Drag N Drop

Game development is hard work but also very enjoyable. Enjoy the process. Know your weak areas and either hire someone to handle that aspect of it or if you are on a small budget you can offer to do a trade. You can do something your are good at in exchange for something you are not.

Other advise
Watch the forums daily. You may pick up ideas and things you did not know.

Use the forum search button. Narrow it down to the category you would most likely find it in so you can get more results. ie To look for information on shaders look in either Shaders or Starting with GameStudio forum categories. Shaders that come up in C-Script and WDL is not going to help you if you are looking for Lite-C.

This forum is limiting for words like LOD as it will not search a 3 lettre word. So go to google and type in LOD and "3D Game Studio" or "3D Gamestudio" to try and find what you are looking for from there. I have done it that way and found information on these forums by doing my short word searches through google as these forums come up in google searches.

Download any demos you see that uses Lite-C and run it to see what it does. Then open the models in MED and see how they were skinned and study how the models were constructed. Go in WED and look at the behaviour tab and see what script they are attached to then look in SED and study the code to see what drives it. You will learn a lot that way.

You can search google for 3D models as there are quite a few for free out there or even inexpensively. If you are going commercial make sure to read the license agreements.