That rust looks like my SD, mine is a tad worse. Looks like a lot of work, goodluck.

Those are really simple welds... no reason why you can't do it and learn as you go. You just want decent penetration. I am always concerned about the rust coming back when it's that bad. Guess I am not convinced any of the rust "treatments" actually keep it away.

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08 R320 CDI current

Past
95 E420
87 300D Turbo 5spd
90 300TE
83 300SD
85 300TD
92 400E
85 190D