Jim
you say you have flex track that you were told as code 100,
to my knowledge, code 100 is NOT used in n-scale.
also, you stated that someone said that it looks more like you have code 83 track,
both code 100 and code 83 are common to HO scale
as you've posted in the n-scale section of the forum, please check.
if you have trains that came with your track,
chances are (i'm guessing) that they may be HO scale,
and so, you wouldn't want a n scale jig...
now, with n scale,
the most commonly sold rtr track is code 80.
with handlaying in n-scale,
code 55 will run virtually everything.
whatever you choose,
do post pics of your progress
we all love pics here
btw, welcome to the fast tracks forum