I have an old 1989 Wellcraft Scarab that has 2 rot issues I need to address. First, there is a removable floor panel over the fuel tank that has gotten soft in a spot. It looks like moisture intruded through a gouge that was in the floor and over the years it rotted. Like I said, it is removable and it looks like the cause is from the top, not the bottom but I am no professional. See picture attached. I was thinking of covering it for the winter and then in the spring taking the whole panel out and having new plywood cut and glassed over.

Second, all the way at the end of the bow of the boat in the cabin, there is some rot/delamination right under the tow hook. It looks like water got through the tow hook over the years and rotted the tip of the stringer. How do you suggest I fix this? Should I have it addressed ASAP or is this something that can be addressed in the spring? I have checked the rest of the stringer system under the cushion in the cabin and everything seems solid (for a 30 year old boat, anyway.)

Any advice on the best way to address these issues would be appreciated.

I would get it all done over the winter if you can. Why wait until Spring when everyone is busy??
What happens when you remove that panel and find more issues??
Did somebody store an anchor in the bow?? Its gouged all over.

you can try to use Git Rot. Sold in many stores including Walmart. You need to drill a couple holes around the rotted place and inject it in. The compound penetrates into the wood and if like you said rot area is small, will solidify the wood and prevent it from rotting further.