PS3 Pre-purchase questions

ok, i'm getting ready to buy a PS3, but there's some things i'm unclear on that i'd like to get straightened out beforehand.

1.) Will playing on a non-HDTV have any affects on the quality of the graphics and if so, how severe?

(I have HD at home, but not at school)

2.) What would I have to do to connect the console to a wireless network?

3.) How necessary is it to buy an extended warranty?

1) The Graphics still look really good on SDTV, but they are just not high def.

2) The Ps3 has wifi, so all you have to do is change the internet settings to wireless.

3) My Ps3 stopped working after a month, so I regret not getting an extended warranty. The Ps3 warranty is one year though, but be sure to have a proof of purchase and be careful not to void the warranty or else they charge you for service(I think $150).