Suzzeee:
If you're anywhere near Mount Vernon, there's a truck-driving school in town (Biddix) that might be a place to start asking about lessons. They may have branches elsewhere, too.I was fortunate when I took a post-Boeing-retirement job as a transit coach driver for Skagit Transit and their instructor taught me about diesel pushers.
Driving a 40-footer on our express service through downtown Everett in evening rush-hour was scary the first couple of times, but it got me over the "hump" and our MH is no problem, though at 32-ft, it doesn't really qualify as "big".