Wow,
That's a good question. ! The very first thing that came to mind is make SURE you get an up to date MRI of your spine B4 getting the implant....in case they need to refer to that regarding your issues with upper cervical.
We can't get MRI's after getting the implant.

Someone here (can't remember who) was implying that they were gonna get a dual lead implant, one lead up higher than the other to cover cervical and the other lead for the lumbar.
Others have successfully had 2 implants.....
I'd make sure you have good communication with your medical team and have the plan all layed out on the table (and in writing!!) ...i'm a biggie on that, because I've seen too many times when a patient was told ONE thing, yet in reality their chart was different.

The medication question is a good one as well. I remember having a fit over how i was going to manage during the trial and trying to determine if it was working.....but honestly.....it all just 'works out'......you know your body and you'll somehow 'know'.....even if you have to try and cut your meds way back for a short time to determine if pain is decreased in your lower body.
Hopefully your Dr will coach you thru this.

I'm sorry you are having such a bad pain day.
Flares still come.....and to this day i do not comprehend what i do or don't do that triggers a 'bad' day.
They suck.

Hang in there
Rae