I have a sprint activated PPC 6700. It is in perfect working order.
I plan on getting the case and screen fixed of any minor nicks and scuffs with my insurance plan.
I do not have the box but have a home, data cable, car charger.

I would like to sell it to buy a newer/different phone. What would be a good asking price?

What needs to be done on my end to ensure the buyer can activate the phone. thanks

I'd call Sprint and just verify with them that if someone does buy your phone, that they can reactivate it. As long as it's not reported stolen, the ESN shouldn't be bad - but who knows if they require the purchase of a handset to start a new account, etc.

As for price...I'd say $225? $250 at the most? I haven't looked at used pricing so that's just a guess. Just put it out there and see what offers you get.