If he got the regulator into your alt, you're fine, I'm sure. I'm not an electrical engineer, but I suspect this part is pretty generic.
Use your cluster test (see youtube vid by SolidJake) and see what voltage you're getting with car off and on...should be around 12.2-5V when off and around 14v when on.
I'm so depressed. No one wants to come see me in NYC: Sat, Oct. 8, 6 p.m. at Greenwich Village Comedy Club.
Mangofy your E46!