Decom Old Exch Srvr and Install new....

I currently have 2 exchange servers in my AD schema, i just installed a new exchange server (new hardware, etc) and i want to remove my old exchange server completely from exchange schema/ad schema.
but i dont konw how to do this properly, i've already migrated all my exchange mail boxes over to my new mail server, and if i shut down my old mail server everything appears to run fine, except it still shows up, nad i'm afraid it has some roles on it that i need to migrate over... any help would be awsome!

thanks