Our distance was quite a bit shorter. We bought sight unseen (ordered a new build) from a dealer about 120 miles away. We did this because that dealer was probably $4,000 less than the best price a local dealer of the same camper would offer.
So, as others have said, we drove down, did the PDI, and fixed the one issue we discovered (a dump valve handle was not connected.) Then we camped for the weekend at a nearby campground just to enjoy the new camper, and just in case...
Hint: New campers might really STINK until they can air out for several days. Be ready for that! (Ask me how I know LOL.)
We had zero issues...
As for the inability to get service locally...
I've seen this argument over and over and I don't get it. If I'm running a service department, and I can get a factory to send me money, I'm gonna do that... If I have a customer willing to spend their money with me - I'm gonna do that. I guess if it's a really small place where the service guys are very close to the sales guys you might get that... Frankly speaking, if it's just a spite thing, I don't want to do business there anyway. If they are just so busy that they put their own customers first... Well... I can't argue too much about that and it would have to be factored in. I'm betting most places don't care where you bought it. They have service techs to pay...
In my specific case I had no need to worry. The dealer I bought from was about to open a new branch about 40 minutes away from me...