Welcome to iboats! We will guide you through getting this fixed right up.
"Closed end aluminum rivets" is the key. These are rivets desiged for boats. Replace the missing rivets.
You could bent back the dent but, I doubt it will stay that way. You could rivet a piece over the dent or have it cut out and a new piece welded in.
The items that you are going to be friendly with are: Pop riveter with closed end rivets, 3m 5200 sealant, and your best friend will be Gluvit.
Gluvit is a 2 part "flowing" epoxy made to be applied to the inside AFTER your repairs are done. It will seal the seams and tiny leaks.
Got any pictures of the dent and the hull? Look at this link to post pictures
http://forums.iboats.com/bbBoard.cgi...7;gtid=1179789