How do I transfer someone else's account on hand-me-down iPhone?

[NJRonbo]

I gave my brother my original first generation iPhone
when I bought the second generation.

My brother's original iPhone has just died so I want to
give him my first generation 3G phone.

Problem is, I can't get rid of my information on the SIMM
card and overwrite it with his.

His information is backed up on a secondary computer.

I figured, okay, I just reset my phone and then sync it
with his iTunes account.

Doesn't work.

Is this process as simple as just switching out the
SIMM cards? If he puts his original iPhone SIMM in
my 3G phone will all his information be transferred
and he will be good to go with his own number and
programs?

Thanks in advance.