Roadrunner, I've never had a problem with getting any parts for my chassis. If it is workhorse specific, I use Precision Sales and Service in Birmingham, Al. They are a Workhorse Dealer and have shipped me anything I needed.
Winnebago also has been helpful in the past, though it has been a few years since I talked to them, so I don't know if that has changed or not. But any Winnebago dealer can order you just about any replacement part. Some things won't be available due to age, but normally a replacement of that part with a newer one works fine.
I have found that a RV Service Center or mobile tech is usually faster, better and cheaper than a dealer service center. You can literally be hung up in the dealership for months.
When I purchased mine 4 years ago, I treated the chassis like a used car. All fluids, brake, transmission, radiator, rear end were changed. All filters replaced. New serpentine belt and idler pulley. New chassis battery. New tires were part of the deal when I bought it.
As time moved on we did UltraPower upgrade, iridium plugs, magnum wires, flat screen TV's, etc.
We've put about 30,000 miles on her over the last 4 years and except for a few minor hicups, she has been problem free. I understand the anxiety of making that large of a purchase, but would encourage you to give it a shot. We have no regrets. BTW, we do not fulltime, we are snow birds and use the coach to see family and friends in the mid and southwest.
Tom and Gloria 2017 Newmar Ventana 4369, TOAD: 2015 GMC Canyon, Blue Ox Towbar, Baseplate and M&G Braking System