Seems to me... (as an outsider in most respects, I feel ultimately that I have the highest authority in this case
) so here goes.
I figure there are a couple of categories of owners: one who will tear up, tear apart, move around, modify or dismantle just about anything that rests, resides or even slows down on his or her property or within their grasp and the other type is mortified at the thought that they'll mess something up and they'll never touch it even if they're supposed to for visual inspection or minor maintenance.
For the first category, the installer of whichever kind of service or equipment just does their best, gets the owner to sign off on the project and hopefully collects their pay. Going above and beyond the call of duty might include taking a couple digital pics (which may prove to be your saving grace in the future if a problem arises due to their dabbling), providing some sort of instruction (as to maintenance issues, codes that apply, etc).
The second category only requires your card, the offer to come do a free annual safety check (or discounts on whatever maintenance is necessary) and a handshake.
For both parties, there's some wisdom and headache prevention to be found in one of the things gov't buildings are known for - tape on the floor that denotes a "DO NOT DO ANYTHING IN THIS SPACE" warning. Those that dabble will happily remove it and those that don't will step around it as if it warned of the plague.
I tend to pick and choose the things I dabble in and electricity is one I don't mess with. I'll tear into just about anything as long as it's unplugged (watching out for capacitors, too) but not necessarily with the expectation that I'll be putting it back together and hoping it'll work much to the dismay of the telephone guy who left a spare phone at our house when I was a youngster
(boy, was I in trouble that time!).
I don't mess with plumbing at all and a clogged sink can unravel my day in a hurry!
And natural gas equipment, my furnace for example, takes some courage to even light and can 'eat my lunch' when it blows out in the middle of the night.
[This message has been edited by BuggabooBren (edited 09-09-2002).]