Consolidated "how-to" for this job:
1. Remove necessary throttle linkage and vacuum lines, remove valve cover, remove air cleaner housing.
Just as you would for a valve adjustment. Removing the air cleaner gives you excellent leverage for the rocker towers.
2. Remove the three (or two) hex-headed capscrews for the rocker assembly you're removing.
These take an 8mm hex key.
3. Rotate the engine by hand to the "sweet spot" where the rocker assembly you're removing doesn't have any cam/spring pressure.
The best spot for the aft group (set of three) is pictured. The exhaust valve for the No. 3 cylinder is at the 12:00 position.
4. Pry up to remove the rocker assembly from its guides (one guide per tower), then lift out.
A medium-sized flat-head screwdriver, as shown, worked well with a little bit of force.
5. Rotate the engine to TDC for the affected cylinder.
The cam for the intake valve will be at 11:00.
This prevents dropping the valve into the cylinder when the nuts are removed!
6. Remove and replace adjustment nut and lock nut.
I used the "third wrench" to compress the valve spring while initially threading on the lock nut. After both were on, I used valve adjustment wrenches to compress the spring so I could get the rocker assembly back on.
7. Rotate the engine back to the "sweet spot" for rocker assembly re-installation.
8. Push rocker assembly down onto guides.
Ensure that they're lined up, or they won't seat. Tap them in with a small dead-blow hammer.
9. Coat threads of 8mm hex-head capscrews lightly with crankcase oil and reinstall hand-tight.
These should turn by hand until seated. Resistance indicates that the rocker assembly is not seated properly and should be reseated.
10. Torque 8mm hex-head capscrews to 38 n-m (28 ft-lb).
11. Adjust the affected valve.
Might as well do them all while you have the cover off.
12. Reinstall air cleaner, valve cover, linkage, and vacuum lines
13. Have a beer!
Or two. Responsibly, of course.
Thanks to everyone for all the advice and help on this job.