You are an exception. Not everyone can work on their own cars and those that have to do for themselves are better off with a platform with as much support as this forum offers and is as simple as possible. Unless he is willing to outlay the cash for a scanner, or software for a laptop, adding computer diagnostics to the mix only increases the complexity and cost of maintenance. Hence it won't be repairable by him if anything diagnostic wise goes wrong. He's obviously handy enough with a wrench so the mechanical aspects are a given, regardless of which platform. I spot on nailed that as confirmed by later posts about putting the trans in his Jeep, I see his type all the time. They can fix their cars up to a point and then just need a little help, guidance or diagnostic work. Now mark this: I rarely if ever see your type. It's a rare customer that knows what the hell he's doing, so why would "you" be coming through my door? We are not talking about you, I was judging his abilities and skill set. Can he learn? Of course he can, it's nothing demeaning about the OP, just a gauge of where he's at technically.
I never said there was anything wrong with the platform , the drivetrain, called them apiece of shit or any such thing. I don't like them. I think that they look like gay, cookie cutter garbage. Hence my "whateverthefuck car", which is about anything in the 90's. Auto styling as a whole took a fucking nose dive and you could barely tell one bubble car from the next, it's a whateverthefuck car.
If he's talking about getting rid of a car over a broken rocker arm for an "unknown" car, as was stated "the devil you know is better than the one you don't". This was before I saw the rust pics, but all too often I see people ditching cars with a major problem that's repairable only to get another car that "runs". What they pay in taxes, registration and insurance would have fixed their fucking car! This wasn't even anywhere near a major repair.
You are not a typical car owner. You have extensive firsthand knowledge of that platform and drivetrain. You aren't even an enthusiast, more like a connoisseur. You summed it up with one line "They have virtually all had the profile gasket replaced by now, but it's smart to ask."
I have no idea what a profile gasket is and most likely neither does the OP. I'm sure everything I need to know to repair it is in Mitchell or Alldata. Can I fix it? Yeah and most likely so could the OP. Can he fix everything on the the E36 like he can the E28? There's the sticking point, you are adding a whole new skill set and tool set for the diagnostics. Not just any diagnostics but European diagnostics, which not every shop will handle and does not have anywhere near the support as Domestic or Japanese. For something that old, yeah it's there and getting cheaper all the time.
So what crap was I spouting? That it would need to go to a shop for repairs? Most likely unless he has a scanner/software and the capability to use it. That most general repair shops won't touch euro? I know shops that don't even do ELECTRICAL!
Do I have the experience to back up everything I said? Yeah I do. That's what you called me out on and what I took offense to.
So you can work on cars. Big fucking deal, a lot of us can.
I'm not a grease monkey, and I'm not a mechanic. I'm an Automotive Technician. Just like your PhD, I went to school for this, I go to classes to keep current on technology and diagnostics, I read technical data for fun, and every day I have to hit a moving target, on the fly, in any automotive system, regardless of make and model. It is a big deal, it's the difference between putting on a band aid and a brain surgeon. I know a lot of "mechanics" and guess who gets called when the shit gets thick? Guess who fixes what no one else can fix? There's a guy down at your local shop ready and willing to jump around like a monkey with a hard on, and just like a monkey he'll throw shit at your car all day long and call it fixed. Guys like me on the other hand, we wrote your technical manuals, and I'm glad you can follow, it gives me hope that there are people out there with more than a lick of shit between their ears. I don't mean that as disparaging, quite the contrary. As a kid I learned from my grandpa, my friends grandpa, my dad...they were men. They could fix anything, no fear, just care, patience and common sense along with the persistence to do the job right. I look around at the halfassed shit that this entitlement era brings and to know that common sense isn't dead is a great thing.
Skilled technicians are a dying breed, not really dying so much as the auto repair industry is hemorrhaging skilled techs to the IT fields. Why bust your ass for less than stellar pay, abuse your mind and body to exhaustion and still get treated like a thieving leper when you can get paid more, sitting in a cushy office, with benefits and vacation for the exact same diagnostic ability? I used to love it, now? I'm jaded and tired. Attitudes like yours are a large part of the reason, and no, not everyone can do this.
No, really. 
Bitch I'm breaking for lunch before you can even untangle your panties.
. Oh well, I kinda like the e28 better than the e24. I think it has something to do with the taillights.
