OK, I'll put in my 2 cents, M.
If yer just going to stay in the neighborhood, no farther, only... I'd go electric.
It's quieter and u won't tick off the neighbors.
If going further, I'd get one of the least expensive kits from the vendors, get some experience with them, and then decide what you might really like to have. You'll always be able to get your investment back, for a well assembled MAB, especially with your qualifications. Takes about 4 to 6 hours to assemble one, if you want to do the speedy method, a couple days if you wish to follow Alf's instructions on pre-inspection and such, which is the wise choice.
Schwinn is dandy... any chrome-moly frame the motor will fit in is good for normal use.
Brakes are the big issue, IMO.
A motor assisted bicycle is like going downhill, ALL THE TIME. Especially in traffic!
Brakes a very important!
There's any number of details that can be discussed, but you probably can't go wrong.
Especially at this time of year.
With summer coming up, you may be able to make money selling built-up bikes.
Good job for an old duffer, huh? :-)
My goal is cheap, reliable, personal transport, below the tax collector radar. Fun counts for a lot!