[DonC]

Phil:
Had a similar episode with my big block a while back but in my case it was just a seep of coolant coming from the block/head joint. Was advised by the builder to re-torque the heads and that cured the problem. Hasn't come back in 20,000 miles since.
The explanation I got is that the difference in metals between the iron block and the aluminum heads can result in a little bit of "squirm" between the two materials that will show up over time.
If I remember correctly I just backed the head bolts off 1/4 turn reversing the tightening sequence and then re-torqued in sequence.
For the rocker shaft removal I backed off the bolts 1/4 turn at a time until they were loose and then removed the shaft. Putting it back in I ran bolts down finger tight and then did the 1/4 turn routine again until the bolts had brought the towers down into solid contact with the head then proceed with tightening to the proper torque. Because the rocker shaft is under spring pressure as you're tightening take up any slack by hand in the other bolts before doing the 1/4 turn.
DonC