I have the 95D190P, so very similar to your unit, but don't know the exact differences. It's an easy enough job to do, but important to get it done correctly as any leak can be dangerous.
Here is an article that helped me understand RV propane systems: Avoiding the Pitfalls of RV Propane System Failure
(by RV Doctor).
First, to know if it's possibly the pressure regulator, one easy way is to see if your burners work correctly. If they work fine, it might not be the regulator, but it still could be. Also, if the burners work but your heater isn't it also could be the valve to the heater, the thermocouple, or thermostat.
Mine uses the Marshall Excelsior MEGR-291 2-stage regulator and is found inside the plastic covering next to the valve, located behind the access panel which is the driver side step. You just need to confirm what yours is and replace with exact or similar - exact will be easiest. If using similar, the biggest issue is making sure that the vent is pointed in the same direction (down) and the fittings are correct.
I might also suggest replacing the valve at the same time because I've seen plenty of posts from folks who say their valve leaks a little (as mine did) when not fully open or fully closed (probably valve packing). I can't find the info on the valve right now, but will look around, but I remember it was pretty standard. I've also read a number of postings that suggest it should be replaced every 10 years (and carry a replacement as many recommend).
If you use similar, make sure it's set for 11 column inches, the most common. Most come preset (although they all have adjustments).
Once the tank is empty (if necessary, have a professional vacate your tank), replacement is fairly simple. I had to remove a plastic covering to get to mine and it was easy enough to undo all the fittings and put it back together. Use some (minimal) plumbers putty before putting back together to help prevent leaks. Finally, to make sure there are no leaks, test under pressure using soapy water around every connection. If it bubbles you need to tighten that connection.
My new one also has a port for a pressure gauge
which I added so I could easily see if the system is at appropriate pressure. I had to cut the plastic cover a little bit to make it fit around that. I think I paid another $25 for those parts and gives me peace of mind to check periodically and know it's right.
Since you are a mechanic and fabricator, you will really enjoy your unit. I've already done numerous upgrades and mods, and there is a ton of info out there. I'd suggest looking up Red Rover RoadTrek amongst others for some great ideas.