I ran my old one that way for a while and had bad drive-line vibes. The vacuum motor was easy enough to open up, it's just a crimped flange. With the vacuum motor out, and the canister opened up, the shaft and diaphragm just slips out. I don't think replacing a bad rubber diaphragm would be worth it, but one "might" be made with an old truck inner-tube. I am just not sure how much luck you would have getting the washers off the shaft to replace it.
But all the same, I am very happy, and the dash light even works!