I really wouldn't try. I'm not a body work expert, or even a novice, but it looks like those fenders are a real bear to remove and replace. And even when done by good body shops, 1800's with replaced body panels often don't look quite right.

I would pay attention to that long seal inside the front fenders that blocks off the gap between the inner fender and the outer fender. Just open the hood, you can see and feel how there is perhaps an inch or less tall void between them that stretches from the cowl to the grille. I think in my car's case that they didn't get that sealed properly after the fender replacement, so moisture got access to that large space.

As for the sills, with the carpets out there are some holes in the inside of the car. Ensuring that the drain holes are not blocked is a big part of making sure they don't rust, that and removing blown in dust and debris that will hold moisture there.
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'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)