Diesels are really easy, put in clean fuel, have a good water separating fuel filter, change the oil and adjust the valves at least annually, and turn the key. Should start in a couple of revolutions if it's not cold out and even then with Cold Start function or Glow Plugs, it should start quickly. If it doesn't start quickly get nervous because it may have low compression and need major work. Diesels are no brainer engines with only a little care in maintenance.
It's a tribute to the good old Atomic 4 that so many are still running 50 or more years down the line. Actually it's a much smoother and pleasant engine for a sailboat. Parts, freshwater cooling kits, electronic ignitions and rebuilt engines are still available. A bit more work to keep running because of the ignition system on gas engines and you have to take a little care because of the fuel. Hear of more explosive issues with propane than I do gasoline.
As I stated earlier, there is something to be said for the simplicity of an outboard but they can have issues in rough sea conditions.
If Catalina left the tiller rudder shaft in place for an emergency tiller, changing back to tiller would be a matter of getting a tiller head and tiller, removing the wheel pedestal and filling the hole in the cockpit sole. May even be able to make money if there is someone out there dumb enough to want a wheel. Catalina has a pretty good parts department, may be able to source through them is you couldn't find a used one.
Thanks for all the input folks.
I've been sailing 19-22ish foot day sailers for years, until this summer. All summer I sailed a Pearson 26 with a tiller, outboard, and the traveler aft. Real nice setup, much like sailing a big dinghy. I was really happy how quickly I picked it up. Felt a bit worried until I got out on it - but it was real simple. No standing headroom though, as I am 6ft.
The Catalina has standing headroom, barely.
I think my mind is made up on the tiller vs wheel. I've always wanted the tiller. The problem is that tiller versions are fairly rare compared to wheel steering boats - esp. in boats built in '84 or newer (which is what I want). The 84' and later boats have a more modern interior, internal halyards and other improvements.
Assuming I get a boat with a wheel and don't like it, how big of a deal is it to switch back to a tiller? I can't remember where, or whether, the C27 has the tiller attachment still in place on wheel version boats.
Also, knowing nothing about diesel inboards, I'm a bit intimidated about that. It makes me lean more toward an outboard. The outboard setup on the Pearson 26 was really simple and worked well enough. At this point all of the C27 inboards are ~30 years old or more. Ticking time bomb? You can get an outboard version easily for 5k (maybe less). But almost all of the inboard boats I've seen are 10k or more. Seems like a big premium for a boat with a 30+ year old inboard.