Help Resest my G1 T-Mobile (Please Help me)

[Type-R]

A question, if I reset my G1 T-mobile, you said that I could lose some apps, i'm clear about it...the question is, Dont matter what kind of SIM card I have? because a friend told me that I need a SIM data card but I have a normal SIM 128kb of Claro. Some people said me that i can do it with wifi but i dont sure about it, I wanna confirm.

Help me Please..

Thanks.

Note: I dont know the Gmail password that my G1 have, that's the reason that I want to change it, I want to put my Gmail address.

Thanks again.