Jerry, you do so much building and tinkering that I simply cannot believe you are "unmechanical." That said, yes, pumps do go out. I do know that sometimes, if the motor itself is still running, if it's just not moving water, sometimes you can replace the impeller or some other part and it will work.
My PondMaster "died" last year, and I made a mad dash out to the pond store. Luckily I phoned before I went, to be sure they were open and had what I needed. The owner told me to bring my dead one along. Good thing I did - he was able to fix it, and the price was much much cheaper than buying a new pump.
I did buy a new one, though, to have as a back up, because the patched up one will only last so long. Eventually that part is going to go bad, and then I want to have the right size, good quality replacement ready. If if should die at 5:00 pm on a 98* Saturday, I'd have no way of getting one until Monday - which means a pond full of dead fish. Best to have a spare on hand.
BTW, I picked up two pumps this year at garage sales, one for $3 and the other for $2. They are small, and I hoped to use them on fountains on my deck. But when I plugged them in, they are FAST. Maybe 300gph or more. Way too much for a two gallon fountain. So now these are my back up backups.
Just remember that you need tubing that fits your backup. The two smaller pumps I bought don't have the same size output connector as my 900 gph, so require smaller tubing - and that means adjusters so they will fit my filter, etc.