UPDATE
Didn't get to do much this week other than gazing forlornly at my baby parked next to the spoils pile and rereading this thread...
Wed I figured I'd give it a go. Still not sure what I did or how, but was able to "free" the 4wd lever. There was also a not very good sound of a metal clunck- like something binding up. However, the front seemed to free up, but I sure didn't feel good about driving it and shut it down.
Figured I'd do the 500 hr service and see what happened. Drained 4+ qts from the front axle. OK, a bit low, but definitely not dry. No metal bits or chunks came out with the oil, no burn odor. Had new filters on hand, but hadn't got new fluids yet, so a trip to town. Friday was rainy and I'm not eager to crawl around the wet ground so much since retiring from the army.
Today I attacked the service, refilled front axle, new coolant, engine oil and filter, grease... but reluctant to change out the hydraulics. At nearly $14/gallon, I was very hesitant, thinking, gee what if that gets dumped to fix what's wrong...
Anyway, after doing all except the hydro, asked the wife to come and listen as I gingerly inched it forward then back a few times. All seemed well, no noises, wheels worked. Figured I'd complete the service and drove down to a spot convenient for that.
Although I was about 12 hours shy of 500 hr service due, the hydro fluid looked pretty bad, almost milky looking compared to new. Of course this didn't show on the dip stick. Anyway, changed all the filters, some metal on the plug magnet, but not excessive. I felt with my finger inside but felt nothing.
So now I've worked about 1.5 hours brush hogging and no problems. Still a mystery what the problem was and if it has indeed gone away -- but my fingers are crossed.
Thanks for all the help.
David