Wow. $200 for an oil change. If I lived near you, I'd offer to do them for $100
Is your D90 still under warranty? You can still have the oil changes done by any garage at all.
Put it into Low any time you're on a road you wouldn't drive a normal car. Lock the center diff if you're on a slippery surface.
Crawl under your truck with a can of WD-40 and squirt it up above the transfer case to free up the lever. Don't let it drip into your eyes. This happens all the time to Land Rovers that don't get used as intended. The transfer lever gets rusted in place.