Rachet, I would advise upgrading the psu to at least a 300watt quality psu (Antec, Sparkle, Enermax, PC Power, etc) cause the GF4 supposedly is a hungry beast.
I would expect the warranty to be at least 1 year but it will probably be around 3 years. Some manufacturers have a lifetime warranty, like PNY (I think that's the one). If you find any problems, they will generally show up in the first couple of months and if you have a failure I don't expect it much longer than a year anyway cause you will get the most use out of it in the first year and after that you will either upgrade or it will work fine which is the likely case.