Hi relskid
There are some people on this board who opose learning a language in a class, while there are other who think learning it in a class is an awesome idea. I personally think you'll do better studying it without a class, and just studying smart. You can spend more time on difficult stuff, and the course is more tailored to your needs, but that's just my opinion.

As for learning greek after russian, I guess it would help, but the fact that you learned russian would help you learn any language after. The fact that they have the a very slightly similar alphabet will be of no help in the long run. You should learn that second language because you like it, not because 5 of its letters are the same.