Suzanne, I can not tell you about the lean but here are a few things I do every season:
Easy stuff first..Visualy inspect tires
..tread and side walls for bulges or ware and air pressure.
get wheel bearings packed (regular machanic can do this)
Make sure the hitch is adjusted so it will not come off T.V. by jacking up trailer while hitched to T.V., if T.V. goes up too your all set. Also check condition of safty chains.
Make sure gas bottle (and Battery
if on tongue) is secure and will not fall
off and turn gas off.
Check that all lights
Check to make sure door will not open while in transite.
make sure all cubby doors will not open while in transite.
I have seen many threads about the required clearance but if I got in the Boler
and rocked it hard, had wife was to be looking at wheel well and it didn't rub I would say "no worries"
Now get down and dirty (or go to garage and have then lift it for you) and get down under the trailer and visualy inspect the frame for any stress cracks or flakeing rust that may have weakend the frame.
Sounds bad but I find no bad spots on my 80 Boler
so the steel used must have been good.
Gerry the canoebuilder