Kind of hard to get oriented with your pictures, but it looks very similar to the crack/repair we did on my son's Sanger cruiser. Note in the first picture, someone previously tried to "bondo" the crack (gray stuff)--needless to say, it still leaked.

Ground out the bad glass--had to get rid of most of the strake before rebuilding it with new glass

Sanding/smoothing fiberglass work

Brushed on white gel coat

Finish sanding the gel.

After finishing the bottom, we turned it back over, cut out the poorly repaired floor, removed soggy foam, laid several layers of glass/mat to back up the bottom repair, and glassed in a center stringer and 2 additional supports for the new floor. Seems to me that it took a couple of weekends to complete the job. Have 2 seasons on the boat and haven't had any more problems.