My computer is a year to 2 years old(I can't remember which). The graphics card is a Geforce 6800 the processor is a Pentium D 820 2.8 Ghz. 2 gigs of ram and 4 allocated from hard drive space. I have 3 hard drives, 160 gig, 200 gig and a 300 gig. My question is, should I be thinking about upgrading my graphics card, and is there some way I can upgrade the processer either by overclocking or something else if I want to continue to play some of the newer games coming out for pc?

You could upgrade your video card and your processor, as well as your MoBo.

overclocking is mainboard dependent, contact your main board manufacturers and ask them if your main board supports overclocking.

only after that you can proceed, but if they say no, then sadly that puts an end to your overclocking journey

is the mainboard manufacturer the same as the processor manufacturer? Second: is getting a new processor as easy as taking the old one out and putting a new one in?

No the motherboard manufacturer just makes the board.The processor manufacturer is the company (Amd or Intel) who made that.And well if you can do a quite accurate placing of tiny pins then its pretty easy to replace a CPU.Its just lowering it onto some holes.And lowering a latch down.

even if you could, i down reccomend overclocking an Intel Pentium D, nor upgrading to a faster one. they run VERY hot, and use a LOT of power. i reccomend keeping the processor, and upgrading the graphics card