Hi, after many years hidden in a cupboard I have found my Original Mod. 6G M, still in the two part polystyrene box and yellow cardboard sleeve. It has the twist sleeve around the barrel that makes it easier to cock. The spring/s still feel very strong but a fired pellet hardly travels twenty feet so i presume the seals need replacing. Is it worth having this work done? if so where? or should I just sell "as is"? Any help or suggestions would be appreciated.