Rich,
I just picked up my first two Webers used this spring and I have been looking at a lot of them. I am with J, an 18 WSM in the great shape that your is in the PA/MD/VA/WV area is right around $200. With the cart and the side burner that would increase the price. There was another WSM 18 with a pitmaster IQ for $275 on this site recently out in CA. My guts is with J and KE. I would start at $300 and not take less the $275. Good luck selling it keep us in the loop, this is a super cool piece. 
Michael