I've been on 6 weeks of vicodin/percocet - what withdrawal time should I expect?

Depends. It depends upon the frequency, strength of the medications.......Mostly hyperalgesia for few days....But not much. Vocidin is not a strong narcotic but Percocet can cause withdrawl but again total dosage during 6 weeks is the important factor to decide whether you can have withdrawl or not.
Minimal. Withdrawl after only 6 weeks should be minimal. If it occurs will last a few days. I suggest you wean off medication by a pill or so every few days rather than just stop.
Wean dose. I suggest not stopping all at once. We the dose back by a half to one pill per day every 3-4 days until you are off. If you must stop "cold turkey" expect withdrawl symptoms to last 5-7 days.