You can buy neoprene replacement packing seals for nearly any cylinder from a seal house or hydraulic supply. They are a floating style and seal w/o taking up the entire space originally used for the packing which is what the spacers you describe are doing. Just give them the ID/OD or take the old parts int to compare. Very inexpensive too. The bushing you referred to are just what you suspect...guide bushing to keep it centered in the outer tube. Probably held in place with steel stop rings. In the top of the cylinder there is probably a bleeder screw to bleed off air when you fire it back up. If so you might want to replace those as well as they get pretty gummed up. All are cheap parts.
Sounds like your right on top of this repair. Good Luck.
