I have had the two leaks you described.
The top slide seal was not properly caulked between the seal and the exterior wall. They removed, cleaned and recaulked. Has not leaked since.
The front pass-through hatch leaked at the frame. I removed it, cleaned, caulked and has not leaked since.
As far as damage, dry it out as quick as you can. I have had many leaks over the years and nothing rotted away. You just have to address them asap. Ignore a leak and your camper is doomed.
Don't stress over it. Repair and Enjoy. That's part of the game.