When I bought my Sud this year I had No intension of getting any of the welding done at the "local" garage.
Reasons are simple, most garages quote hundreds of pounds for welding as most the time it will involve removing carpets, wings Doors etc. In practice they don't bother and "tack" weld around and apply shed loads of underseal
They won't cut out the old rusted metal - they just use a bigger repair panel so the rust keeps eating away, they won't even treat the new repair plate to any kind of rust protection just good old underseal
For the amount of welding I need to do to mine (and yours by the looks) It is cheaper to BUY a mig welder and do-it-yourself at least you'll do the best job you can rather than a skilled welder cutting corners
and you can always sell the mig after
I have "had a go" at welding my rear wheel arch, and honestly I think I done a good job at the time, BUT after doing some more you learn better ways of welding (I can see myself cutting it back out and doing it again)
SO have plently of practice before you start (don't just weld new metal as its a lot easier than doing the cheap crap fitted to the car