Welcome to the Enterprise.
Don't be discouraged. Opto issues are a rite of passage for all STTNG owners. Fixing our pins is a very rewarding part of being a collector for many of us. And it will be well worth it. Fantastic machine!! Its complexity is much of why it is so darn cool.
If you haven't already, I suggest getting the This Old Pinball videos. Repair guides are available online as well. RGP search feature is also your friend as about every imaginable issue have been previously discussed. (I hope it is ok to mention the "other site" on here)
Good luck,
Shawn