I am looking for any general tips of info in replacing an existing (15+ yr
old) Flint and Walling (F&W) 1.5hp well pump

the well and pump is only for sprinkler water

am I correct in thinking that I should be able to just purchase a new motor
and leave all other parts untouched, especially since they still work fine?

is the "motor only" replacement harder than a pool pump "motor only"
replacement?

reason am thinking it's time for the replacement is that on a few occasions,
when pump is started, it causes a white smoke coming from motor (I normally
shut it off for a few minutes) but I suspect that may have to do with the
priming as it then runs normally once the water level is up at ground level

Generally when the pump is getting ready to go you will know it by the
sound that it makes (bad bearings etc). white smoke may indicate an
electrical problem. you might want to have someone from a pump company
come out and take a look at it before spending the bucks on a new pump
motor.