hey there, Very brave diving into advanced level building so soon but then you may be real good.

What you can do is create a grid of blocks in WED, say 10 X 10 medium, large or small.
Then create an empty file in MED 'block_grid' or something and save it empty or throw sometthing in like a primitive or 2, it doesnt matter as the file will be overwritten.

Then back to WED and export your grid to .mdl format.

When queried for file to export to, choose the empty one you just made and complete the process.

Now then, (dramatic I know) you can manipulate the vertices easily here but limit it only to height contour and not by to great and extent.

When done (obviously remebering the process and what you did) save the back to WED and import the .mdl file back but choose 'Auto' mode for block import, not concave.

All going well, you should have blocks back, next senario; you should have a majority of blocks and a few model conave parts.
Worst case, all you got was what you expected, a .mdl file

In other words, diligence at getting what you want will be rewarde by effort spent.

Now, I dont know if they are actually true 'blocks' but they show up white (thats a block!) and they dont need poly = on etc.

Good luck