Changing caliper

[flyin 5.8]

I haven't seen the rear disk setup but most calipers are held on by two pins/bolts that the caliper slides on and the flex line. The rear brakes also have the parking brake and I'm not sure how those are hooked up, some use the caliper and some are like a drum setup in the rotor. if it uses the caliper you will have to figure out how to unhook it, if its in the rotor you shouldn't have to mess with it. Anyhow, some one with average mechanical abilities should be able to do it.

It sounds like your caliper is frozen, when you take it off, clean any corrosion off the pins and where they go through the caliper
and be sure to lube the pins good with white (lithium) grease when you put it bake together.

You didn't say if you did anything other than 5 lug the front, But if you need a fairly simple upgrade there and are comfortable with calipers check out this web site.
http://svo73mm.cjb.net/