The cowling is removable, though there are numerous fasteners. Things do look pretty tight in there, but no worse than my motorcycle or my car. Indeed, the Mooney engine compartment is spacious compared to either.
It is a bit tight. Unlike some of the armchair, internet Mooney experts in this thread, I actually work on my Mooney myself a lot. Mine dates back to 1966, so just like a 1966 Mustang, or Corvette, it needs work from time to time. Of the certified retractable planes, the Mooney is the least expensive to own, either manual (the least expensive of all) or electric.
The cowling does come off, but it depends on which era, or which model you are looking at as to how much it is a headache. In any case, they are all with the engine very close to the firewall, so there is a compactness there that the cowling has no bearing on. Also behind the panel can be cramped. I work on my Mooney and I'm really glad I have small hands. For me it's not an issue. For guys with big ol' green giant hands, maybe look at another brand.
As to the hangar queen issue, I agree above that it is fleet wide, but perhaps impacting the complex planes worse. Bottom line is, GA is in serious decline and it's pretty obvious once you get out and away from the prosperous urban centers and trendy destinations. People are quitting, or forced out these days and there are way more airplanes of all types available on the market than there are pilots that want them.
This can be an opportunity though, depending... IMO a Mooney (or any brand) that has very low hours and has always been hangared can be a total diamond in the rough
IF it is priced accordingly and you are willing to take on a bit of a project before flying. A low time, always hangared airframe is gold IMO, however there may be ADs to comply with, rotten engines and props, as well as antiquated avionics potentially.
This is why I say "priced accordingly". It's a buyer's market, so offer accordingly. I kind of wish now that I would have taken on the hangar queen project, but I guess the right one never presented itself to me.