i guess that comes down to exactly what you are trying to achieve. i've buzzed stainless bolts and nuts etc on to mild steel on some jobs and it welds real nice. seems to hang on ok too. in some situations it might not be so cool.......
You can weld it with either mild steel wire or stainless wire.to mig stainless you need to use tri mix gas co2,argon, helium.If it is exposed to heat such as exhaust it will rust prematurly due to carbide precipitation but for non structural it will be fine.
What are you attempting to weld? Stainless exhaust tips onto mild steel exhaust tubbing, no problem, for example......
Im going to set in/french a couple of tail lights into the rear panel and im not sure if i should use repro stainless or not or find commercial steel tail lights.
That should weld just fine with regular carbon hard wire, dont worry about the tri mix gas or anything like that for your application just weld it like normal, maybe alittle hotter. On a structural or a preasure type application you would use an alloy fill material (rod, wire, fill rod) usually designated by 309 but for something like that you should have any issues.
Short answer; yes. I work in a food production plant and most everything is stainless, most of which we tig, once in awhile we need to attach mild steel to stainless, and we use mig or tig, depending on the circumstances. Brian