We have the V10 in our 99 Holiday Rambler. We have about 42K on ours now. Almost all the new gas burners I've seen are Fords. You would be very much limiting yourself if you don't look at the Fords!
That being said, I've had one problem with ours. We were going on vacation last year when we came up on a heavy rain. Luckily we were in the middle of Nashville. Our coach slowed down and wouldn't get over 25 MPH. Turns out in the early years of this design the air intake snorkel would suck water into the filter and collapse it. When the air shuts down, so does the RPMs. A new Motorcraft filter and we were back on the road. Now I keep a spare. I hear there is a fix from the factory, but my local dealership isn't aware of it, if it still is available. As far as blowing plugs, that was very rare. Mostly involved the 5.4 V8 in 1997. The 6.8 is the 5.4 + 2 cylinders.
Now to your mechanic - if you stay with the same guy (and sometimes its a close friend or family) and you have problems, you will get a lot of "I told you so"s. If its a deal-breaker, go diesel!