You obviously do not
understand the operation or design of the circuits enough to do so without a
high probability of damage to the set.

You misunderestimate me. *Of course* I don't understand the circuits
enough -- yet. I'm not going to do a damn thing until I do, and until
there's a much lower probability of damage to the set (preferably
hovering around 'nil').

What I really need now is not dire warnings, but more information
about either the circuits themselves, or where to find the
information. I know service manuals exist; I'd like to know how to get
one. I'm educated, bright (enough), and cautious. I'm not going to
mess anything up, because I won't touch anything until I'm pretty
positive I'm touching the right thing.

One observation: TVs suck. Computer monitors (and I mean *all of
them*) have allowed the end user to adjust just about every damn thing
-- including horizontal width, of course -- for at least about a dozen
years. This is not rocket science, it's just crappy engineering. The
fact that I've even got to consider some dangerous hardware mod just
to get the whole picture on the screen is ludicrous.