OK, I have swapped front axles a few times and it is simple if not a little laborious.
A few things you need to consider to avoid any snags.
If you still have the original front axle it will be the low pinion that everyone dumps in favour of the high pinion pre-2000 version. I assume you too will swap to a high-pinion but as you are already lifted by 3.5" according to your specs then you shouldn't have any trouble with the driveshaft hitting the exhaust and if it does it will soon modify the exhaust itself.
I also assume you have the correct hubs and rotors for your 2001 XJ? If you do then you will need to do one of two things if you swap to an older axle.
1, Get the rotors with the axle you pull from the junkyard or buy a new set for that junk axle.
2, Swap the hubs from your 'bent' axle onto the replacement so you can use your own rotors. Here's a few tips on swapping hubs and shafts complete - http://www.jeepforum.com/forum/showp...6&postcount=13
As Bikedude said, no need to break into the brake system at all, just pull the calipers and tie them up out of the way then re-fit them to the replacement axle.
Don't re-tighten the control arm bolts until your vehicle is back on the ground and rock the jeep before you do tighten them so the bushes are settled in a static position. Tightening the bolts while your truck is up in the air with the axle drooping means the bushes will be twisted when you lower onto the ground.
If you are up against the clock then leave the new trackbar install to a later date, it won't be any harder to do and you won't be rushing so are less likely to make a mistake.
Popping the TRE's out of the knuckles is easy. Remove the pin and nut then place a longish bar between the knuckle and drag link and put pressure on to try and split it. Then get your hammer and hit the knuckle where the TRE fits hard. A couple of solid taps and the TRE should pop out without damage.
Once all is bolted back in then you need to re-check your tracking to make sure the toe is right. You can easily do this yourself, see here - http://www.go.jeep-xj.info/HowtoAlignment.htm
Make sure you get the right ratio, you don't want to be doing it again in a few weeks (ask me how I know
) although it is quicker the second time!
Oh yeah, I'll come and help you but you will have to cover my flight fromthe UK!!!