Hey gang,
I just bought (another) BMW. I-- Just-- Can't --Help myself!

Except this one, is a gorgeous 2005 545i with low miles (ish, 90k) that I picked up for $1500. Apparently the previous owner called a 'mobile mechanic' out to his house to address runability issues (misfiring, etc) via coil packs and spark plugs (which didn't fix it). The mechanic took the ecu claiming 'water damage' (I have photos of this, which look legit; but honestly could have been downloaded from the internet). I suspect injector issues and the mechanic ran for the hills when the dip---+ didn't know what he was doing.

Anyhow, now I need to buy this car a new ECU. With that, I have 2 questions:

1) eBay has a LOAD of them, ranging from 199 to 900 dollars. Anything specific I should look for??
2) Do you have suggestions for BUDGET resources to program the ECU to this specific car?

THANKS IN ADVANCE!!

~George