OP, can't you just find a stock exhaust for cheap and install it? I'd never dream of removing the stock exhaust from an e46 m3. If I had an E46 M3 and someone with a super sprint or whatever said hey i'll PAY you $1500 to install this on your car i'd say no!
Just my opinion of course ;) I think the M3 is a masterpiece and should be kept pure. I think you're just SOL on this OP. time to move on.