[Bent]

I have a 51 series wide screen CRT type RPTV, it's overscan is a bit high, it's focus is a bit off, and it's convergence is slightly less than perfect.

I've read of the service mode convergence access codes, I've even entered the service mode once.... but lost my nerve prior to changing anything.

How difficult is a service mode convergence routine on this set, how long will it typically take, and how likely is it that I may screw up to the point of not being able to return to where I was? (I'm not interested in doing any colorometry work, as I don't have the measurement equipment, but I'd like to get better focus and convergence.
Can I perform mechanical focus with a picture (grid?) being displayed, and while I'm in there, would it benifit from a cleaning (lenses and 1st surface mirror?, - it's never been opened in 6 years.