A valve job usually means refitting the existing worn valves, the casings are honed round and straight, the valves electroplated with nickel or if very worn copper to build them up and then nickel and lapped to the cylinders. Some companies in the past could supply a set of oversize valves as replacements that only required lapping, Selmer France had at one stage an identification code on their valves so a replacement could be ordered. Replacement or a sleeve for a cylinder would be practically impossible. I have never had a valve job done on any of my trumpets, I have several that a purist would consider need one, the one with the worst wear is a 1950's Besson 10-10 but still plays well. In my opinion valve alignment is more important than a bit of wear in the valves. The air pressure in the horn after the mouthpiece throat is very low. Regards, Stuart.