The good thing about practice week is that you've got all day to explore the Island before practice starts at 6.15pm - roads close at 6pm. Probably the best thing to do is stop by the info desk (welcome centre I think they call it...) at the sea terminal, where you'll be able to pick up info on all the touristy stuff.

You won't need any kind of parking pass for the circuit but the towns tend to have 'disc parking' zones, which are free of charge but there may be waiting limits, so you need to display your disc. You can get one of those from the welcome centre too.

How long are you over for?