hey there, welcome to the forum!! if u r lookin for some nice German and Russian figures, Tamiya, Dragon, DML have some really good ones. tyr to find their newer kits, they are better made. and some of Tamiyas kits have a good nuber of them for ur use.
another thing u may want to add is which units were involved in the fighting there. this would require a fair amount of research though, and you may not want to spend so much time and energy on that right now. still, its a good consideration to look into such info when u get older and can focus more on that type of stuff.
as for the base, depending on what size diorama u want to build, u could just go down to your local arts & crafts or trophy store and pic up a nice plaque for normally just a couple of bucks, less than ten is the usual price, although it goes higher for larger bases. just coat them once or twice with a stain or varnish to color them, and sand in between.
as for buildings, there are several different companies who offer wide ranges of buildings. stick with city or urban styles for this particualr diorama, since its in a city. companies like Verlinden or Custom-Dioramics have some very nice offerings. u can buy them at ur local hobby shops, or order them via catalogs, or the internet. try to get them from dealers rather than the prodcer themselves, I think its cheaper. heres a couple good ones:
http://www.vmdstudios.com/tw_shows.htm
http://www.discountmodels.com/
http://www.squadron.com/Index.htm
http://www.hometown-hobbies.com/home_page
http://www.rollmodels.com/
hope it helps. BTW (by the way) there's a group build for junior modelers that going to start in a couple of days on the forum. basically, we go ahead and start building at the beggining, and try to finish the project befor eht eend of the build. check out the site on the forum:
http://www.finescale.com/fsm/community/forum/topic.asp?TOPIC_ID=25684
see ya round the forums!!