Dell has a nasty habit of using proprietary motherboards/cases, so upgrading that is near impossible. You still have a pretty solid system, and a 475W PSU should still be fine for most cards. You should be able to go ahead and pick one in your budget and be fine, if the specs on that link are what you have.
could you reccomend an appropriate video card to be used for Maya?
budget under 400$,
I tried adding a Sata 3 expansion card but it didn't seem to take well with the Dell bios,
I'm concerned about using video cards that are not recommended for my system,
is there any way to make sure a video card will be compatible with my dell system before I buy it?
There's probably no way to know 100% if a card is compatible if Dell has stopped updating their list. With Maya, you'll want to stick with AMD since they're known for better compute power than NVidia. A 7870 would be an excellent card within your budget. http://www.newegg.com/Product/Product.aspx?Item=N82E168...