[Roadsters] Timing issue

[Ken & Tammy Williams]

Hey,
First, I'm not much of a mechanic.  Keep that in mind while you read.

After doing some various maintenance on the roadster last week (including
plugs, points, condensor, and tach cable seal), my timing got way out of
whack.    The car was running great before.
I had the motor and transmission reworked 4-5 years ago, and embarrassingly,
I've never messed with the timing.  So... we got the timing adjusted, but it
had to be moved to the extent of its adjustment.  I'm not sure if it is full
advanced or retard, but either way, it's got no more.  The group helping me,
came to the conclusion that the distributor is off a tooth.
So...How does this happen.  One..Did the mechanic who did my engine work
several years ago put it back together like that? or Two...Did something else
happen to allow the distributor to jump a tooth?
Remember, I'm not much of a mechanic.  Sorry if this belongs in the stupid
question dept.
Second part, do I just go through the motions of re-setting the distributor,
or is there something else I need to be concerned about?  The car is running
great since we adjusted the timing.
Ken
'67 1600