Rust!, rust! not so glorious RUST..... etc sigh

[BHadley]

Ello,
Looked at my rusty tub of an e30 318is today after nearly two years of loosing the will to bother with welding.... can’t seem to let it go so I need some advise please.

I have 1x drivers inner arch, outer arch and a outer sill repair piece that is a pattern cover sill.
What Bmw call an outer sill is the main structural area where the rear jacking point is. If I bought this Bmw terminally piece (which looks like the whole outer sill less the quarter panel join/ sleeve over) would I have to remove the door to brace the shell or Can I ”apart panel”a and mig weld it to what’s currently there?

I can weld, just out of my depth for the method to do it and dont want a bent shell. Could I just beat some sheet steel into something that looks like it should or make several small pieces and weld them to together then weld that on the car?

See link for pic of what I mean, (the left of photo is the piece I mean) ignore the prices I’m using for reference if I have to go to Bmw for the full lot then so be it. Unfortunately it’s looking like both sides...

https://www.wallothnesch.com/en/outer-s ... doors.html

Thanks for reading I’m a bit stumped...

[BHadley]

The rot is in most of the left section of the picture, jacking tower, the inner sill has been plated all ready.
I walked away for a couple of years not 2 years straight of welding!