Body help/advice needed

Well I finally got to hitting the front lower part of the fenders with the sandblaster to see how bad they really are. Looks like I need to cut out these sections and make patch panels and weld in place. As I've said many times on this forum I am by no means a body person so I am going to need some help getting this done. Below are some pics of both fenders, with inside and outside pics. How much do I cut out and when making the insert to be welded in should it fit inside the cut tightly or need to leave some space for weld to fill in. What is the procedure to do something like this. I'm counting on this group to get me through this!
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Thanks Rod