Tom, be sure to go to the bike trial info link, open the map PDF, and flip to page 2. Pretty generic, not-to-scale map, but shows the tunnels and bridges.

At the southeast end of Bridge 218 (west end by timetable), there's a nice little viewpoint where you can sit down and share your lunch with the local chipmunks. They will be all over you if you have some peanuts, granola, etc.

The need for good, bright headlights on your bike and/or helmet is critical if you plan on biking through the tunnels at any sort of speed. Also bring plenty of water and snacks in a backpack or saddlebags. If it's a hot summer day, you should still bring a warm layer to put on for the summit tunnel. Close to 40 different interpretive signs to stop and read along the way, so plan on taking several hours if you really want to soak it all in.

Oh yeah, near the mid-way point of St. Paul Pass Tunnel is a sign marking the MT/ID border. Good spot for a fun flash-lit "I was here" mugshot.