SKS and "accuracy"...
Having been to a couple of Appleseeds myself (and shot Rifleman @ my first) and having some experience with the SKS, I'd have to say that an SKS would not be my first choice for an Appleseed. FWIW, the Appleseeders with SKS's whom I have observed, didn't shoot so well--this may be a skill question, but partly it could be the fault of the rifle.
Now, it depends much on a couple of personal factors. There are SKS's and SKS's--If you have had yours to the range, been practicing, and know that it'll shoot well for you, then go for it. Lacking that kind of experience, and/or having a different rifle with adjustable peep sights, or a 'scope, I'd go with the non-SKS rifle. If you aren't an experienced centerfire rifle shooter, and have an autoloading .22 with peep sights or a 'scope, THAT would be what to bring.
Removable magazines are VERY handy--bring at least two if your rifle uses them. The SKS non-removable magazine, you can feed from stripper clips, and that is about as fast as changing mags--IF you have the stripper clips.
Centerfire rifles are more costly to feed, and an Appleseed does burn up quite a bit of ammo.
You ALMOST MUST have a sling on yr rifle; w/o one, you will still learn a lot but you will miss out on much. If your rifle has sling attachments, the Appleseed people will probably have a sling you can borrow or buy.
Now, having said all that, an Appleseed is very much a "Bring what you got, shoot what you brung" event. If what you have is an SKS, bring it.