Replacing Parking Break Assy

[Rich72C10]

I have a new parking break assy and had its pedal pad move to the right so it can clear my new kicker speakers. I have a 72 C10 LWB 350/TH350 and hoping to get some advise on how to remove the old one and get the new one installed. The currently one is fully installed (with everything around it installed) and working properly.

Things I think I know:
1. Remove the two assembly's firewall nuts
2. Remove the underside assembly's nut/bolt on the dash.
3. Likely loosen (or remove?) 3 driver side dash bolts - to loosen the right side of the dash?
4. Push / slightly knock the Break Assy to the right to get it out.

But before all the above I am pretty sure I need to deal with the Brake Assy cable. I know there is a cotter pin/clevis pin attaching the parking brake line to the assembly but I assume this is under wee bit of pressure (even when the brake is not engaged). Do I just go underneath the truck, driver side, behind the transmission and loosen the adjustment nut to gain some slack?

I have read and found a few posts on removing the assembly, which is where I got my 1~4 "things I think I know". Though I haven't found how to best/properly do the parking break cable.