We were in Alesund on the Koningsdam earlier this month. We also rented a car through Avis, a few months in advance. It was a very easy process. We drove out to Trollstigen via Andalsnes, then back around to the island of Alnes to see the lighthouse, go to the beach, and then back to town. A gorgeous drive all around. Trollstigen was fantastic. We had a manual transmission, which, IMO, is far easier to maneuver in this type of driving to control speed. The road itself is pretty hairy - there are a few spots that are for one vehicle only, and we had 2 buses trying to pass each other. It took a while and traffic became very backed up. But, the view at the top was amazing, and the drive down the other side was very pleasant.Your route sounds good too. Is there a map to show the route you took?
I have reserved a car at Avis too.
Thanks a lot for the useful info.