The most up-to-date guidebook, dare I say it, is
this one and you can read parts of the contents on the website for free. I'm not aware of any access problems with any of the routes since publication late last year. There is someone on the island keeping an eye on the routes in the book, and so far everything is OK.
Walking through the mountains in February should be superb, but bear in mind that it can rain at that time of year, and it can be misty on top. Most of the time it should be nice and sunny.
As for wild camping, just make sure that no-one catches you and you'll be fine. Local people do camp in the wilds, but as most the the terrain is private property, you have to keep out of sight. The only real campsite on the island is a rather bare and dejected looking site near Lluc Monastery. There are some newly-opened mountain refuges, but if you intend staying at them, you'll need a pretty good command of Spanish (or Catalan if you really want to impress) as I'm told it all has to be done by phone with credit cards.