It's not _mad_ difficult, but it's not a cake-walk either
Get her up as high as you can.
The pads: Remove the anti-rattle springs first (most times easy, once I found them a complete bugger!)
There are two adjusters on each of the rear callipers, you will need to retract both pistons to get the pads out. I could go into the procedure here, but you're better off to download the manual from Craig's site here Craig's Place, Alfa 75 Manuals and Information
Group22 Brakes. Take note that one of the adjusters on one of the callipers works in reverse
To get the discs off you then need to disconnect the driveshafts at the transaxle. These are held on with socket-head bolts, and you need to treat these carefully and with respect.
AFAIR the V6 is similar in practice to the TS, but slightly different in detail, it has a spacer between the tranny and the disc I fink.....
Anyway, refitting is reverse of blah, blah, blah......
As regards tightening the callipers back up, I am inclined to ignore the 'feeler-gauge' approach as difficult to get satisfactory results with. I lean towards "tighten them up, then gradually release until the dics is just rubbing" I find this quicker and more effective.