To be totally fair, not all Ford dealers will work on motorhomes. The dealer in Columbia and Silver Spring will not work on them, but the Mt. Airy will do some minor maintance if you plead with them. Frederick will do anything and everything Ford related to them. Given where you live this might be your closest dealer.
My concern would be when traveling, and I have a chassis problem, will I be able to find a serving dealer within a reasonable distance. This goes for any motorhome chassis including the big boys.
The Frederick Motor Co. is 6 miles from our house -- that's where I bought my car (they sell Subarus also). That's a good sized facility and very old -- almost 100 years I think.
The service issue is definitely a concern for RVs in general, and particularly the Sprinter. IIRC, someone on the V-N Yahoo group figured that worst case a Sprinter-based RV owner might find themselves 300 or 400 miles from a service facility.
Of course when assessing risk, it's important to look at the probability as well as the severity of the risk. It is human nature for all of us to assign wildly varying degrees of weight to various risks that we all face. The _probability_ of something happening is often disregarded. Take people who have phobias -- the risk of stepping outside and being bitten by a rattlesnake or a spider is pretty remote for most of us, but there are people who obsess about that.
I'm not sure that's comparable to getting service on a Sprinter-based RV, but I'm sure you see what I'm getting at. Yes, it certainly possible that a person might need a 250-300+ mile tow to a service facility, but how likely is it that any modern vehicle will become completely disabled? Most, including the Sprinter, are pretty reliable these days. If that does happen, it probably won't be more than once or twice in the first say 100K miles. If/when it happens, what are the chances that the person will be in the absolute worst spot in the US, or more than say 150 miles from a service facility?
I'm not saying it's not an important consideration -- it is, even more so than with the Ford-based RVs -- just that in the overall scheme of things it doesn't seem to warrant the amount of attention and weight some people give it.
Now, having said that, we will of course suffer total engine failure in Minot, ND. ;-)