I thought about rebuilding the vacuum pump myself.

After weighing all the possibilities and the costs to do so, and the risk of a bad component getting introduced, and the cost of a failure, the $300. for a new one can be considered a bargain. I expect the SD to go another 100K miles and I don't want to be thinking of all the issues that can fail on a rebuilt pump.

Now, if I can just find the time to install it............