I don't think anyone is making remanufactured PSE pumps.

Getting at the pump is easy.

At the bottom outside corners of the rear seat lower cushion, you should see red levers - down where the seat cushion ends and the carpet starts.

Those release the front latches on the bottom cushion. Pull (or push) the lever and lift gently at the corner. Then do the other side.

Once released, slide the lower cushion forward and remove it from the car.

This is a one-man job - the cushion is surprisingly light.

The PSE pump is in a well beneath the sound batting on the passenger side of the car.

If you're blowing fuses to the pump every time you insert one - the pump is likely shorted out.

As others have stated, most reputable mechanics provide a 12/12 warranty on their repairs - parts included (providing they buy the parts).

As for MB honoring the warranty on the part if it was purchased there - they likely will, providing you can provide proof of purchase.

Note that your invoice from the mechanic is not sufficient. You must have the invoice for the purchase of the part itself.

As for MB honoring the labor part of the deal - I highly doubt that. I'd love to see some proof of that. Knowing that MB has recently had a habit of dodging legitimate responsibility for items they caused (140 wiring harnesses, 210 spring perches, etc.), I find it hard to believe that they would pay to replace a part someone else installed.

The effort to install this part is literally 15 minutes MAX. Cushion out - 30/60 seconds. Uncover pump - 5 seconds. Detach vacuum lines - 2 minutes. Disconnect harness - 10 seconds. Pull pump and replace with new (it's not bolted in) - 60 seconds. Reattach all harnesses and vacuum lines - 60 seconds. Replace rear seat - 5 minutes (after reinstalling it and realizing you left the seatbelt latches below the seat).

Sit down and admire your handiwork - 4+ minutes. Done.

You're most likely the victim of a mechanic that purchased a used part and charged you like-new pricing. My 92 has the original part, and it's working fine. (knock on wood).

You can make this repair yourself... just be careful how you pry the vacuum lines loose - you don't want to break anything.

If you haven't already done it - and I know I've suggested it to you before - get an AllDataDIY account for the car. Register through the link on v12uberalles dot com to give the author of that excellent site a few cents referral fee. After all, you own a V12, too...