Is it the old 200 Miller? If so it is one of the best wire-feed welders ever built. They still bring $1000+ at auctions around here. I've been offered brand new welders in trade for my 200 but I still own it. I have a 304 now but the 200 is an AMAZING back-up machine that I still use on occasion.
I like 75/25 gas for mostly new metal and a few repair jobs. CO2 works better for dirty metal but the welds aren't as pretty and it's hard to control splatter at higher amps. I tend to use the stick for ugly projects or outside projects.
Get a 220 rig at the highest amperage you can afford as the projects will always get bigger. A 120 machine would be handy with some .023 wire for the thin projects. .035 gets tricky with under 16ga. material.
My ideal welder for a hobbyist (I've been one for many years) would be a 200+/- amp rig that runs on 220 since you have it and the ability to swap .035 wire and .030 or .023 wire by simply swapping the rollers. I think 75/25 gas is worth the expense but my $0.02.
x2, especially on the unimix gas.
