Unless an animal replaced the valve seals earlier in the engines life you should not have to worry about the threads that hold the rockers in place.
1) Remove valve cover
2) Remove camshaft oiling tube
3) Remove 1 thru 5 rocker assemblies
Caution: (watch shims on the valves, keep in order)
4) Place compressed air into the cylinder being worked on
Caution: (Engine will turn as air pressure builds)
Use valve spring compressor of choice to R&R springs
5) Replace valve seals
6) Reinstall shims to their respective valve
7) Reinstall rockers 1 thru 5 (hand tight using 1/4" drives)
8) Remove rocker 6
9) Replace valve seals than reinstall rocker (refer to step 7)
10) Torque the 8x1.25 bolts to 12lb/ft
11) Reinstall oiling tube, dab blue loc-tite on securing bolts
12) Reinstall valve cover with new gasket
When I do this repair I work cylinders 3/4, than 2/5, than 1/6, it minimizes the number of times the engine rotates. As well leaving rocker number six in place while working the front five is a preferance.
Seals, two different diameters
Shims between lifters and valves
Try sticking with ¼ drive ratchets for reassembling the rocker assemblies.