I'm jumping in late on this late, but just in case you didn't go on your trips, I figured I'd figured I'd pipe in. You can buy tickets in advance online, or you can call up to the day before to make your reservation.
I used Starline for transportation only to Hollywood (this is not the five hour tour--just round trip transportation). I called the day before to make my reservation. I was picked up at the Grand Californian at 8:25 a.m., and we then went to the
Disneyland Hotel and Paradise Pier. I'm not sure how many stops were made before they picked me up, but the bus was pretty full.
After loading passengers at Paradise Pier, we went to the Starline Tour Center, where we had to check in and transfer to another bus. The bus I took dropped passegers off at Universal, and then took us to Hollywood. We arrived around 11:00 a.m. (so it took about 2 and a half hours to get there) We had about five hours to explore Hollywood on our own, and then the bus picked us up and took us to Universal City Walk for two hours (which was disappointing--I would have preferred more time in Hollywood). We left City Walk at 6:15, and it took about 90 minutes to get back to the Grand Californian by the time they dropped everyone off at their resorts.
While in Hollywood, I took a one hour tour on Starline for $15, and thought it was a great little tour that gave you an overview of Hollywood. You could not get off the bus on this tour. I purchased the tickets at the kiosk in fron of Graumann's Chinese Theatre.
I went to Hollywood a second day, and took the Amtrak train from Anahiem Station. I posted more detail about my transportation to and from Hollywood on this thread:
http://www.disboards.com/showthread.php?t=2646035