Yeah - digging around the guts of an amp can kill ya.
Instead, I got one of these bias probe gizmos from WeberVST...you plug your tube into it...the plug the gizmo into the amp. The one I got (cheap!) requires that you already have a multimeter (which I did). The other models have an LED readout to see the bias measurement.
http://www.webervst.com/bias.html
Anyway, it's very easy - no danger of getting killed (although watch your fingers on the hot tubes).
Someone on this board can tell you the recommended setting for your amp...but that's just a guideline. You can adjust a tad up/down to see if it sounds better with your amp.