So I found a plane that appears to be in pretty good condition. The engine was overhauled 100 hrs and 4 years ago. Thing is, it was a field overhaul by an A&P. Would that be an immediate dealbreaker for any of you? What kind of things should I be asking him about it if I move forward?

Thanks!

Don't get too concerned about field overhaul ,if engine has 100 hrs on it in last 4 years -that's good. Have through Prebuy of whole aircraft.

I was excited to find an engine with low hours overhauled in the last decade, and which is flown regularly. Without exaggeration, 95% of the planes I start looking into have overhauls from 94-96, with low hours. Must have been a good few years for the 90s for the engine shops!

Everyone thinks their plane is a gem and don't care about low hours over a long period. I found it funny when one of the guys cut his asking price by half after a couple weeks because he realized his engine was junk from non-use.

I plan on doing a pre-buy that is the level of a full annual inspection. Would rather spend a little more now, get a really good look, instead of buy into a polished turd. It appears that over the past 10 years, he has kept making little improvements, rather than letting it go to waste.

0-300 sounds like a old 172 or 170 Cessna . Both decent airplanes in there own right - looking at your past few post I see you also invited wife to go with you to see other aircraft .I'd get a rental 172 with her and kids , fly to a bunch of airports within 80-100 miles and see lots more aircraft .Normally aircraft that sit on tiedown for months on end are not advertised -but just as "for sale" with right approach. Cash talks and will bring out those folks that would normally not be interested in selling there long lost relatives airplane. Everything(aircraft) I have is completely paid for no financing here I own several property/ houses and only one has mortgage left.

I wouldn't worry about a "field overhaul" unless it was actually done out in a field somewhere. Quality of build is much more important. I had the C-145 in my old 170 OH'd about 13 years ago (my, how time flies!) by an engine shop recommended to me by the local air taxi outfit's DOM. Turned out it was a one-man operation in a little funky hangar....but that engine was still running great when I sold the airplane 1100 hours later.
An OH is kind of a crap shoot-- I've heard of engines OH'd by name-brand shops and with great logbook entries and yellowtags out the wazoo coming apart inside of a couple hundred hours, and heard of others OH'd by the local mechanic, and with an "overhauled engine this date" logbook entry, going to TBO with no problem.

I've been looking at a bunch of planes and have seen a bunch of basket cases. This one finally has potential and just happens to be nearby. It is a late 50s 172. Seems like a nice way to get around while I build an RV7. I can't take renting anymore.

I know of a plane that got a brand new factory 6-cylinder continental and blew a rod through the case 5 days after the warranty ended, so I agree about no guarantees. Just trying to mitigate the risks.

It being a local airplane is good. Do you know the owner, or any of his friends or airport neighbors, or maybe his IA? What's the buzz on it? Word usually gets out if someone has a lemon he's continually having trouble with, or if it's just barely squeaking through it's annual every year.
The other good aspect of a local plane is that it's easy to go see, maybe more than once, so you/re not gonna feel pressured into purchase due to having bought a one-way ticket all the way across the country to go see/buy it.
If the airframe & engine are in good shape, and the price is right, it's pretty hard to go wrong with an early C172.