-Since you're going to be replacing the tie rod anyway, one trick is to screw the castle nut on and give it a few whacks with a mallet. Before removing the tie rod ends, I'd recommend breaking loose the adjusting nuts on the tie rod. They like to stick and it's easier to put some leverage on them while still attached.
-There's no problem with removing/installing the drag link with the wheel turned, just make sure the steering wheel isn't moved while you're doing it.
-It doesn't have to be perfectly level. Generally if you have a lift kit with 3 inches or more of lift, you need some sort of correction (drop pitman arm or raised steering arm) to maintain your steering geometry.
Just did sway bar bushings the other day with the ORD kit. I've replaced drag links, tie rod ends, ball joints, steering box (with Redhead Gear). I swapped the steering shaft with one out of an early 2000's GM van to eliminate the rag joint. That eliminated a lot of noises and steering issues. One thing to remember is that if you do ball joints (or are unsure when they were done) is to torque the alignment adjuster to spec and measure the drag on the knuckle to make sure it's within factory parameters. If it's set too tight or too loose, it can really impact your steering. The truck is now lifted on 33s, and while it doesn't steer like a new car, it rolls down the road about as well as you could expect such a vehicle to do.