John welcome to the forum! Making a decision between gas and diesel is like the Ford/Chevy debate. A gas coach will normally be cheaper to purchase than a diesel.

I have a diesel, the first diesel I've owned and I really like the low end torque that a diesel delivers. The rear engine makes it a little quiter going down the road.

If you decide on one of the coaches above I would have an independent serivce tech go over the coach front to back and top to bottom.

Check the date code on the tires any thing older than 6 to 8 years will need to be replaced. Tires can be expensive, 22.5" can run $600 to $800 each.

I'm sure others will chime in with additional info.

Diesels can be more expensive to repair but if you do regular maintenance their bullet proof.

As far as maintenance it's a little more expensive but the intervals are further apart. On my Cummins 400 ISL an oil change is once a year or 18,000 miles. The Allison trans is 240k or once every 2 years. I'll never chnage oils on mileage just time intervals.

Change the filters oil, coolant, air and fuel at recommended intervals. Drain the fuel/water separater a couple of times a month or so.

it sounds a little daunting but once you get your head wrapped around the process it's just not that bad. I know because I had the same issues but I'm starting to relax around the diesel.