A lifetime of mechanical experience here as well - and I'm here to tell you I would NOT trust myself to do a proper inspection on a DP I was considering. They're different than the cars/trucks/bikes/boats/planes/STUFF I'm used to working on! For what it cost to have a PRO, that's used to working on these things have a look at one I was seriously considering is money well spent/sleep well at night insurance.
Just the chassis. I can handle the rest myself....
Second, DP's, in my experience, may not accelerate like you might expect if you aren't used to one. They remind me of a turbine. You put your foot down, and wait for it. If you aren't observant/careful, you may look down and find you're going much faster than it sounds/feels just a little bit later. A lot of this of course, depends on what you're looking for. If you're one that needs big power, go for it. My point is, don't blow off a 300 because it doesn't give a 1st impression of a lot of power. Our 275 hangs right in there and has never left me wanting - even in the bigger hills while pulling a toad.
1997 37' HR Endeavor, 275hp Cat, Freightliner
03 CR-V Blue Ox, Ready Brake