I saw that one - it's in nice shape. When it arrives you'll see a small cardboard tab at the rear of the box. If you pull up on this you'll find a compartment under the pistol where paperwork may be stored. Sometimes sellers have no idea to even look there, so don't advertise some of the additional items that may come with a pistol. Yours originally came with a "Model 78g Owner's Manual", blue warranty card, and a pink paper that was wrapped around the barrel advertising the dangers of residual CO2 in the pistol. You may get lucky and find some of these papers stored in that compartment.
As for rebuild kits, I've also purchased a variety of them from Crosssman600Repair as mentioned above. I've started using rebuilt exhaust valves in my 78g/79g and Daisy copies rather than the white one that comes in most kits.
JGAirguns.biz offers a valve rebuild service for $21, They're good people to deal with!
There are several good videos on Youtube that show the disassembly, seal replacement, and reassembly process. As for tools, only one special tool is required, and that is used to access the small seal in the piercing assembly. This can be made with a flat tip bit and a Dremel. Here's a pic of the one I use along with some of the seals that came out of my first rebuild.
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