Would not worry about it. When you take the oem muffler off they cut right next to weld. The new muffler is bolt on, if you want to put the old one back on they just re-weld right next to the old weld.
You would'nt even know it had been re-done, it would only take 30 mins each side.
When I sold my old M3 e46 the buyers wanted the new muffler anyway, told them the car was $1,000 more with the new muffler because it was worth $2,000 when I bought it.
Once you put that new muffler on you will never go back to the oem one.
X5 F15 M50d White, 20"rims, Yellow Calipers, Ceramic Pads. Better off saying what it does not have and that's a B&O Audio System, otherwise all option boxes are ticked.