No, yer friends list will be fine.
But, the easiest way to get yer new 360 on-line again is to go to https://login.passport.net/ppsecure/uisecure.srf?lc=1033&id=66262
Go through the steps to set up a .NET PASSPORT - what this does is link yer new account and GAMERTAG together. When you go to get on-line with your 360 you will enter your gamertag and your .NET PASSPORT PASSWORD, so it can identify YOU and do like an account recovery