Replacing the seal where the pump rod exits the body of the pump isn't a big deal, and the seals
are available at any industrial seal supply house. The pump rod doesn't wear noticeably, so leaks
are due to wear and perishing of the lip seal.
It's not even necessary to remove or completely disassemble the pump. Use a padded vice-grip to hold the rod and unscrew the T handle at the top. Then unscrew the seal body using an adjustable wrench on the hex that is molded into the body. Using a small drift, drive the lip seal out of t he seal body. This is the hardest part, and usually results in destroying the old seal. Take the (possibly mangled) seal to the industrial supply place for ID and buy a new one. cost is in the order of 2-3 dollars, so buy a couple!.* Clean the cavity in the seal body of any debris and put a bit of grease in the hole. Drive the new seal into place, using a socket wrench of slightly smaller diameter or use a bench vise as a press to push it in place. Put a bit of lube on the threads of the body and on the rod, then slide the body down over the rod and screw it back down. Replace the T handle. Done...
Down here in Oz, the replacement pump costs around 200AUD, so replacing the whole unit every time the shaft seal
starts to leak is painful (at least to me). Learning
to do this simple rebuild is worthwhile for the cruising sailor.
* If the replacement seal has a metal spring inside, ask the vendor to replace it with an o-ring (a common procedure). The springs deteriorate in salt water
and cause the seal to fail. Some seals have stainless springs, but even they fail too soon, so the o-ring is a good substitute.