No, MS 2008 wouldn't be deleted and yes it should still work.
However, the question is what do you think you will get out of upgrading?
I run Snow Leopard (and Lion, and Mountain Lion) and Mavericks and really there is nothing you can do in Mavericks that you can't do in SL, except run the latest version of Xcode and developer software to run on the latest machines.
If you're not developing software, I really can't see any advantage to upgrading to Mavericks. It has a few bells and whistles on it, as well as a few gotchas (like some 3rd party software will need to be updated or possibly even upgraded to run on Mavericks).
Basically, my rule is if your computer works fine and does everything you want it to do, forget about upgrading till you (have to) buy a new machine.