hey scott you spelt xterra wrong, haha
calmini lift is a simple as changing a tire. new shackles and new torsion bars,
maybe a bracket or two up front. i did one a year or so ago and it took about two maybe two and a half hours. the only thing that sucked was moving the exhaust to get the new shackle in on the driver side, but it is not that bad.
Not quite that simple, you replace the upper control arms as well and I would buy all 4 new cam bolts as they tend to sieze to the bushing sleeves and sometimes need to be sawed out.
I personally would not use the "heavy duty" torsion bars, everyone I know that has them has had them settle and must constantly adjust the ride height. I have had mine lifted for almost 6 years and still have the stock torsion bars on and they never need to be readjusted.
Proper ride height is critical to getting it aligned properly.
The upper arms are 4 bolts if i remember correctly... ...4 bolts.
As far as the torsion bars it is a personal preference my buddies never sagged at all. but i have heard that. just remember not to use a air gun when you adjust the torsion bars cause it will strip out the bolts and then you are in for more work.