Hi.
I'm pretty new to fixing cars. This is the hardest repair I've tried. I'm trying to replace my '92 940 wagon rear springs. I've managed to get the bottom part of the spring loose (sorry, i don't know the terminology), but the upper part is stuck to the chassis with a rusted bolt/nut.

(bigger pictures below)
The bolt is welded to the chassis, and in a pretty bad condition. But the nut is completely rotten.

My question is, how do I proceed?
It seems to me that the only thing to do is:
- cut (grind) the spring to make some room
- cut (grind) away the nut, remove the spring gasket/holder
- possibly remove the current bolt and weld a new one

I don't really want to do any of this. I don't even have welding equipment. Is there any better solution?
Thank you

(bigger pictures https://imgur.com/a/4duC5 )