That engine sits in a bit of an inverted bucket when it's in a motorhome so the heat tends to get to things over the years. I found that all my vacuum lines were pretty crumbly so it's worth changing them out while you're doing the belts. There aren't that many, but a couple of them are long runs to the front.
The coolant temp sender for the dash is located on the side, right between a couple of the logs on the exhaust manifold. Not sure why that's a good idea, but that cooked mine at one point so I replaced it - you might want to check and make sure nothing's melted and the wiring isn't likely to rest up against the manifold.
You've already found out how the exhaust likes to leak.
The one and only time that an oil filter gasket stuck to the engine for me was on my 454-equipped P30 motorhome. While it is pretty exciting to look out the side mirror and see orange flames and black smoke, I don't really recommend it.
Yours may not be as bad as mine, but my oil fill tube is freaking impossible to get to without dumping oil everywhere. If I have the doghouse off anyway, I pull the tube off the valve cover and fill the engine directly. Most of the time, though, I use one of the cheap HF "fluid transfer pumps" to pump in the fresh oil. I've tried all manner of different funnels including the ones with hoses on them and I have not found a single one that actually worked.
I have heard stories of fuel pumps failing which requires the tank to be dropped. In an emergency, I'm told that the generator's fuel pickup can be used with an external pump.
Something chassis related: Front camber is a function of load on the suspension. I made the mistake of cranking my front airbags up which made the ride so much smoother, but it also created massive amounts of negative camber. One trip to Florida and back later (or maybe it was Gulf Shores, I don't remember) I managed to completely destroy a pair of tires which upset my "buy a tire every year" refresh plan a bit. I can't remember what I have them down to right now but I think it's just a few psi above the minimum pressure from Firestone. And speaking of pressures, the ones listed on your VIN plate are useless. You should find the chart from the tire manufacturer and set your pressures based on the axle weight. Or at least take a guess at what the axle weight might be.
Also on the chassis, they made a half-dozen different versions of these stupid things so finding parts can be a pain. So far, it seems like "gm parts giant" does a good job of matching my VIN to the actual parts and then I can use that P/N to search rock auto or FLAPS for the correct part. So far, the only thing that I've found that is hard to find and/or expensive is a bit of my steering linkage. Otherwise, the parts are easy to find pretty much everywhere and not tremendously expensive. I'm putting new pads, rotors, calipers, and hoses on my front brakes for under $300 in parts.
If you're still running the 8R19.5 tires, those are getting harder to find. I'm in the process of going to a 225/70R19.5. I'm going to cycle them in two at a time - the first two went on the front, I'll get two more towards the end of the year and put all four of the metrics on the back, and then next year I'll do two more to replace the fronts.
I've had really good luck with Good Sam's roadside assistance in both the motorhome and in my regular cars. The only downside is that their towing service is to the closest shop that can work on the vehicle. If you want it to go anywhere else, you've got to pay the overage. That said, when my Excursion blew a tire on the highway - and I discovered that my spare had a cut in it - one call to them and they found a shop that would sell me four new tires at a reasonable price and get them installed that day and then had me towed there. The only reason I sat on the side of the road for two hours was that I didn't discover that I needed a tow truck and not a tire changing guy until the TCG showed up and I realized that I did not, in fact, have a spare tire for him. Best roadside service I've ever had, overall.
Greasing the front wheel bearings doesn't take a lot of time and is probably a good idea.
Double-check the inside tires in the rear for date codes and cracking. When I was shopping I found a surprising number of instances where the outer tires were brand new and looking great while the inside ones were dangerously old.
Back to the motor..... They also respond pretty well to new plugs, wires, distributor cap, and rotor. All the heat that builds up under the doghouse doesn't do any of the ignition components any favors. If you've got the Banks Power Pack installed, you'll have a K&N filter, so clean that up and give it some fresh oil. Check the "ram-air" system, it likes to come loose. I don't know that it really gives you all that much, but every little bit will help I suppose!
