It's simple, but there are a few details which will need to be addressed as far as the completeness of the swap.
The lower triple tree on a late-model is drilled and tapped for the brake hose support. You'll need to drill and tap the triple on the older bike, swap the lower triple or find another means of securing the hose. The lower triples are cast iron, so to do a proper job you'll need to remove the triple and put it in a drill press, anyway.
The brake switches and plugs are different. You'll need to cut and splice the plug from the early bike onto the switch of the late bike. Early model brake and clutch switches will not fit into the perches of disc levers, and vice-versa. You can swap the perches, but then you'll have to rewire both bikes for the plug ends in either case.
Your early model throttle housing is oriented differently and your starter button will now point down toward the ground ( under the bars ) because of the master cylinder. So you'll need to rewire late-model right side switchgear to the bike or learn to live with it.
They're all the same internally and all should be the same height when at rest. It's possible someone cut the springs or spacers in the older bike to lower it. I'd put it back to stock then slip the tubes up in the trees if you want to lower it.
There's absolutely no difference in braking effectiveness between the disc and drum TW front ends (trust me, I own both and have tested both for stopping distance, side-by-side.My wife's bike has drums, and if I thought for one minute they were less effective the discs would be on hers). I converted mine, but I wouldn't bother with it again. Slight nod to the disc if you do a lot of water crossings, but I doubt that's an issue with a tracker. The disc setup is a pound or two heavier. If you like the look or prefer feel of discs, have at it, but if you're on the fence about the swap you won't neccessarily get "better" brakes as a result.