+1 on the installation. None of it is difficult if you have the right tools, but you're looking at 2 or more hours per corner to do the spring swap, especially if it's your first time.
When I put in coil-overs and lowered my car, I put in these adjustable rear control arms (the top one) so I would not experience uneven and premature tire wear:
http://cgi.ebay.com/ebaymotors/Adj-Rear-Toe-Control-Arms-Porsche-Boxster-986-97-05_W0QQcmdZViewItemQQhashZitem439e7ed23bQQitemZ290 421920315QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAcces sories#ht_1313wt_1167
They were not from this seller though.