one of the pistons was sticking
are you sure it wasn't just the guide pins that were sticking, that's the case 99% of the time.
otherwise yeah the lines are never hard to get off even for us rust coast people - be sure to use a 6 point socket. take a good quality hand metal saw (they can be quite compact) and you can saw through lines/brackets to make removal easier if you want to take some brake line with it, then you can unbolt at home on your own time.
hang old caliper aside, bolt new caliper in place, prefill it with brake fluid, and then quickly swap the brake line and you won't really need to do much if any bleeding and you'll only have to bleed one caliper.
rebuild kits are like $1 too. remove piston, clean everything up, put back together, it's really easy i just did one yesterday.