Have to agree 1000% with doug, but there are some instruments that are invaluable.
A few years ago I lent my last oscilloscope to someone and never got it back, feeling the loss I just replaced it (surprise surprise, from ebay) with a 50 buck hitchi 40 mhz dual trace v423 job.
Now I'm not a sparky or electronics bod, never have been, never will be, but I bought the last scope because I knew a guy who had one, and used it for everything conceivable, from testing if his engine points were wearing without diassembling anything, through checking HT coils, you name it, always remember him showing "sinusoidal" mains 240 VAC, which was not what I was expecting to see on the screen. He then got into electroplating and anodising at home, and used to scope for that too... an astonishingly versatile tool.
I can only imagine how an oscilloscope combined with the hands on thing can tell someone like doug everything he needs to know, without picking up a spanner, or resorting to computer modelling or data acquisition.