Shipping boxes with engines to overhaul to the usual suspects all over Europe is a common game in GA. There are only a few reputable shops to do an OH and you hopefully rarely need them. Unless you are very lucky and live right next to one of them, forget about that issue for the initial phase.
You need a mechanic close to you (and not affiliated with the previous owner) to do a pre-buy. I prefer to let somebody do the job, who is taking over the maintenance later on, others prefer an additional pair of eyes - your choice. Get some idea of the quality of the maintenance shops where you station your aircraft and get one of them.