As far as body repairs go, the lower fender patch is actually pretty simple, but there are couple of things people often slip up on: measure before you cut anything - check the fender is straight with pretty good alignment on the car and take some reference measurements from bolt holes, body lines, panel edges. I'll often scribe a couple of datum lines and reference points just outside of the repair area to assist. fit your patch panel before you cut away the original - too many people hack out all the rusty metal then start fitting the patch panel in the gaping hole which makes proper fitment and alignment way harder than it needs to. If you need to trim some of the original fender away to get the fitment close, try to leave things like body lines and braces in place to help 'register' the patch panel. plan your cuts - to do decent repair you'll need to do some hammer & dolly work to stretch the HAZ area, so think about where to cut to make this easy. On a lower fender repair this means cutting the inner brace out, chances are this is rusty too, but you'll need to make the cut at least an inch above the butt join of the outer skin to give you dolly access. Large flat areas warp more so keeping the joint close the lower body is a good idea, but not so close that grinding and finishing the weld is overly difficult. Sorry Giggity but ideally your joint/cut should have been 1-2 inches higher or lower. check it before you wreck it - when you think you've got your patch in the right shape and place, mark it and trim things back so there's about 1/2" overlap of old and new. Bolt up the fender and use strong magnets or sheetmetal screws to hold the patch in place and check fitment. If you really have to pry or push on things to get the patch to line up, it needs more work. This may mean taking the fender/patch on and off at least a few times.