Pgitug
Guru
Well, I'm far from an "expert", but here's my experience with exactly your conundrum.
My previous boat had 2" shafts, with conventional packing glands. It was easy-peasy to back off the packing nuts, twist out the old packing (using a purpose-made packing removal tool), and re-pack. Not positive of the exact product I used, but believe it was GTU Graftex Ultra-Shaft packing from Western Pacific Trading, which allows almost a leak-tight seal, both underway and at rest. All this while in the water.
Yup, water floods the boat while you work. Not as much as you'd think, and easily controllable with your bilge pump, assuming it's properly sized and working. Make sure you have the correct packing on hand before you start. Pre-cut the new packing to size before you begin, so you are ready to install ASAP the old stuff is reefed out. And have all your tools close at hand also.
If you haven't done this before, you may want to get a boatwright to do the first one while you watch, to glean any tricks of the trade I haven't mentioned. It should take about one hour per shaft, so you'd invest whatever the boatwright charged, but might be cheap insurance for your peace of mind.
My current boat has a PYI dripless seal on a single shaft, as well as the rudder post. No leaking on the driveshaft to date, but basically unserviceable in the water, either. My rudder shaft is leaking, and will have to wait for my next haulout to remove and R&R.
In my opinion, I would not replace conventional packing glands with dripless. They cost far more than they're worth.
Regards,
Pete
Just a heads up on your leaking PYI drip less seal. Talk with PYI, don't assume. I had my PYI drip less seal leaking and was told to take some wet/dry 600 grit sand paper, cut into 4"x4" square, fold in half, pull open the seal surface towards the bellows, insert the folded sand paper and drag it around the seal surface two or three times in one direction. This cleans off the contaminants that are causing the drips.