Your Pacific Trawler is equipped with a Tides Marine lip seal on your rudder shaft. All pertinent repair and replacement information is contained in their web site, as well as by phone to the company. They are very accommodating and knowledgeable about their product, and can talk you through your repairs.
I own a 2000-vintage Pacific Trawler with the same setup, and had my seal replaced while hauled. I doubt the seal can be replaced in the water, as the rudder shaft had to be removed to service mine, and the top of the seal is very close to, if not below, the static waterline. The shaft is in two pieces, joined with a welded flange below the hull, just above the rudder, which must be unbolted to remove the rudder.
With both pieces removed and re-assembled outside the boat, I found my rudder shaft was 0.030" out of straight, so I had mine straightened while out. As the shaft is two pieces, getting the shaft perfectly straight is difficult, but the less runout, the longer the seal will last.
In my opinion, Pacific Trawler did a poor job of designing the rudder installation, and chose the incorrect parts to do so. Rather than the three-bearing installation as we have (one at the heel, one above the fiberglass "volcano" where it's leaking, and the third on top of the shelf), the rudder tube should have been extended above the rudder shelf, with only a single bearing and seal at the top. This would have made it MUCH easier to align the rudder shaft (two bearings vs three), and moved the seal above the static waterline, to allow service while afloat without having to remove the rudder to do so. And plenty strong enough to boot.
Oh well, mine lasted 20 years or so, as it appears yours has also. Nothing's forever!