I am new to the world of Peugeots and have been spending a lot of time fixing up "Peu Peu" the 86k mile '89 505 DL wagon that I bought from a good friend back in May of this year. It's a super base model with the only option being an automatic transmission. It didn't even have a radio until I installed one last weekend!
First off, they are durable and well-built cars. Very comfy seats and a soft ride. Reminds me a lot of the '83 Mercedes-Benz 300D (W123) I drove in college. Their rugged reputation made them popular in Africa where a lot of the used European market cars ended up.
Parts availability seems to be hit or miss. From RockAuto I was able to order front rotors/pads, rear shoes and wheel cylinders. They also have other parts like brake master cylinders, ball joints, tie rod ends, brake hoses, filters, tune-up parts, etc. I'm probably going to stock up on some of that.
Some other parts have been more difficult to source. For example, I could not find a driver's side steering rack boot anywhere online so I contacted Peter Holm in Vermont who runs a business called Peugeot Holm where he's been selling Peugeot parts since 1969. He was able to sell me a new one for $20 and I plan on using him in the future. Another issue I had was my center resonator rusting out and the only one I could find in the WHOLE WORLD cost $340 plus shipping so instead I opted to have a local exhaust shop delete it with a pipe for $100. It honestly doesn't sound any different from stock.
I hit up that junkyard in New York that NickD mentioned (his photos below) and had just missed the cars hitting the crusher so I was super bummed. One of them even had what appeared to be nice E-codes.
There were a lot of different engine/transmission combos and some can be harder to find parts for than others. Another example, I needed a radiator since mine was rotted out and sprang a leak. I looked online and could not find one anywhere again in the WHOLE WORLD for a car with a 2.2L gas engine so I had have mine recored for nearly $500. However, for other engines radiators were readily available new for $200 or so.
I paid $800 for mine which was kind of a deal since my friend actually paid more than that for it and put new Pirelli tires and did the timing belt before selling it to me. I'd say that one is well-priced at $1000.
The best resource I've been able to find is the Peugeot of North America Facebook group. Lots of super knowledgable folks on there.
A final thing to mention is that from the B-pillar back the sedans and wagons are pretty much a totally different car. The wagons have an 8-inch longer wheelbase (with a ton back seat room) and a heavy duty solid rear axle whereas the sedans have a IRS setup.
I'd say go for it just as long as you are OK with the challenge/expense of finding certain parts. But they are wonderfully unique and fairly easy to wrench on. I also got the A/C working on mine so that has added to the enjoyment. Being a gas 2.2 auto wagon mine is really slow around town but it's a good cruiser/highway vehicle. I'd imagine the diesel has a similar character.