I've never changed the crank seal or sensor when doing the balancer and never had an issue
as a general rule of thumb, always change the dis module, cam sensor, and crank sensor out together, anytime I ever changed just one the other 2 failed usually right afterward
if your gonna pull the timing cover to replace the seal you should replace the oil bypass valve too
I would personally just swap the balancer and be done with it
are you getting a balancer from dalke?
btw, I'm stealing your sig, one of the best i've seen in a long time