each shock has the one way check valve disconnect point about 10-12" down the line from where it banjo bolts to the shock itself. they are a 2-3" long union of 2 nuts, you hold one end & turn the other & they split apart & the one way check valve stops fluid from coming out.

this is an x-system so technically the opposite corner should be what needs to be off the ground along with the side your working on. however, it would be easier to just lift the whole truck instead of messing with lifting 2 opposite corners.

i will 2nd the suggestion of replacing the xreas entirely, if you have anywhere near 80k miles chances are its shot or not working as good as it should. i just replaced my xreas in my 08 2 weeks ago & even though the xreas had no leaks & was "working", it is night & day difference with new shocks & springs & did not cost that much.