I'm a qualified welder, so any questions, just ask.
As for flux (or MIG/MAG) welders - they are by far the easiest to learn on. I'm trained in stick, MIG and TIG, and I rate in terms of ease of use MIG first, then TIG then stick.
125A should be fine for what you describe, but your shielding gas and wire thickness also play a large part. .6mm wire with argon is my preferred setup for general use, but CO2 and .4mm will be fine for all the smaller jobs.