So I've never flown a GPS approach. I came across this approach into Renton, WA

http://204.108.4.16/d-tpp/0802/05396R15.PDF

It says it's an RNAV (GPS) RWY 15
Forgive me if this sounds dumb but if I have an aircraft with a GPS certified for IFR can I fly this approach? Can I use the LNAV mins or only the circling mins? Why is GPS in parenthesis? Is RNAV simply another word for GPS? I was under the impression that RNAV has to do with some sort of complex nav system only found in larger aircraft.

Thanks