Assuming you already have all of the tools you'll need, I think you already nailed it on the head. 80-90w and gaskets should be all that you need. Might as well do a bunch of maintanence on your axles since your in there (bearings, grease, etc.)
I guess I have never thought about it. Can't see why there would be a problem though. The only problem that I have heard of is in no slip situations, such as pavement, where the tires are different sizes or are inflated different.
You can only find out what shims you need when you dry install the Aussielocker. The shims come in different thicknesses, so you will need to see which ones you need (if any) when the Aussielocker is in place.
I put mine in the rear, the whole thing would have taken less than an hour, but the locking bolt holding the center pin had sheered off in mine, had to drill it out. Took 3 hours.
no press required...and if Toyota has the shims in "stock" locally, they may allow you to purchase a variety of them, then return the ones you don't need. IIRC, they are like $5 each, 4-5 different sizes available.
The shims in question are the one's behind the side gears, which are replaced (not the spiders which are not reused). There is a set range of like 3.xxmm - 4.xx mm of space between the driver gears in the locker. You need to measure the space between and if it is not in spec with the shims you are reusing then you need to get thicker/thinner shims.
Which brings another good point, you will need a set of feeler gauges.
I haven't installed an aussie locker, but, chances are there is a go/no go gauge that you will use to determine if shims are required or not. I just installed the no-slip in my rig and no shims were required.