I think you can DIY and save some money.

On the home page there are articles on PDC retrofits. Use that as a guide as to what may be involved. Depending on the location of the ones that need replacing, you may need to remove the front and/or rear bumpers.

On my 04 removing the front bumper only takes about 30-45mins (no experience with the rear). Do a search as I know I've seen some threads about replacing the PDCs. I know of at least one person who replaced a rear PDC without removing the rear bumper (ca911).

Good Luck!