first, welcome aboard.
second, just spend time going thru the restoration forum, you will find hundreds of threads. just about every iBoater that has a thread in the forum has rebuilt a fiberglass boat. some of us have rebuilt a few
your boat is now 41 years old as they are selling 2024 models. any fiberglass boat from the 80's had rot in the late 90s. assume every fiberglass boat pre 2001 is rotten. generally boats were designed with a 15 year life span back then.
in the 4th sticky down at the top of the forums are all the DIY links. read threads in links 14, 15, 18, 2, 3, 4a, and 4 b in that order. it will give you all the information you will ever need.
expect to spend about $1500-$2200 on materials, incidentals, and PPE as well as 6 months of weekend to repair the transom, stringers and deck before you add a bracket and outboard. If going outboard, I would have recommended aluminum boat and spend $300 on a floor and transom in a weekend.