It's your wallet, not mine, but I would consider using MB-correct materials to redo your seats, particularly if you intend to keep the car for a long time. $1,100 is cheap in the context of the cost of replacing a leather interior for something like a Series-1 XJ6 ($1,100 x 3+).

On a related note, how good is the seat padding, frame, etc? Now is the time to repair/replace.

Remember, the original MB upholstery lasted 30 years. Not bad.