the 1st answer to #1 is in your #3. If it was not recommended to use too many prefabs, it was because too many identical objects might become boring, but taking e.g. phone posts, well, they look the same all the road down, and probably in the next map, too...
#2: I see: You want to make
models, not prefabs!! You could do them with both MAX and Milkshape, where Milkshape as already a MOHAA import function.
#3: If you wouldn't want to use them in other maps, where a prefab might become handy (but not neccessary!), you could just copy those tanks and drag them to where those copies should be.
Generally, I think, you should make clear, whether you want to make prefabs (just a different word for a map file with the enhanced possibility to import it into a map) or models (like those coming with MOHAA, like those vehicles, chairs and lamps). With this information, it'll be easier to help you!
