Nothing to get nervous about, if you don't like the way you wire it up initially you can always change it later. Phase reversal is not for everyone, it gives you a thin, nasally tone that is good for some effects, rhythym sometimes, and some funky stuff. Like a more extreme version of the in-between spots on a strat.
One tip - if you decide to go with a coil tap on the bridge, try and get it so the 'on' coil is reverse wound / reverse polarity from the P90, then it will be hum cancelling when both are on.
Another - practice your soldering on something else first if you've not done it before. the plastic components inside of the pots and switches can melt, so you want to get 'in and out' quickly with the soldering iron and not heat those parts up any mor than you can help it. There are some pictures of very good solder jobs on this board in various places, check them out for hints.
Another - if you want a little bit brighter sound than you're getting, switch the pots to 1 meg from the usual 500k. It makes a subtle difference that can add just a hair more top end to the sound if that's what you find yourself lacking.