New PC + iTunes Library

If possible import instead of copy. It makes for a cleaner iTunes database anyway.

If the path to the files is the same on your new computer as on the old one, I think everything should work fine. Although I do believe that importing a library does in fact preserve playlists and play history/ratings.

Make sure you install iTunes on the new computer before you copy anything (unless your iTunes runs from the J: drive that you're just going to pop in).

When you copy the iTunes folder and its contents, this includes the file "iTunes Library.itl" which is your library database file. This file contains all of your playlists, ratings, and play history, as well as an entry for each song in the library and a link to its location. When iTunes on your new computer reads this file that you copied from your old computer, it will have all the same songs and playlists, and think they're all in the same location, as before As long as they really are in the same location, then iTunes shouldn't know or care that it's on a different computer now.

To change where the database is stored is actually fairly simple. Just copy or move the database file ("iTunes Library.itl") to the desired new location, and then open iTunes while holding down the [SHIFT] key. iTunes will prompt you to choose a library or create a new one, at which point you browse to the file's new location and open that copy. iTunes will always open the last used library when you don't hold the [SHIFT] key, so it will open this one from now on by default.