I've messed with SKS's long enough and want to get a K-31 to restore.  AIM is selling them, they are the only C&R I know of that's got them.  How is the quality?

They are $99 bucks.

Should I spend the extra $10 for a Walnut stock?
Spend extra $10 for handpick?
Spend extra $10 for Sling and Cap?

I've only had good luck with AIM. But lots of others sell the K31. See Shotgun News for a dozen or so.

I've had good luck and bad luck with AIM.  All in all, they'll treat you right, and fix it if you don't like it.  I do get the feeling though from talking to their customer service every few weeks that they get a lot of dick-head customers, and it gets to them sometimes.  I think I've heard some on this board love Allen's Armory's K31s.  They're a little more in cost, but supposedly they're the best in quality.  The great thing though about the K31 is if there is any wear to the gun, any damage, it's usually always cosmetics.  Enough cleaning and refinishing to your like and the gun is almost always a tack-driver.  The swiss never used (to my knowledge) corrosive ammo, so the bores are always in great shape.  I would say order from AIM because you'll get a decent rifle at a decent price.  Just note though, that the majority of K31s have some damage to the buttstock, and if you're lucky you'll get one that doesn't, but I happen to have not been lucky yet

I just got my K-31 from AIM last week, just the regular $99 one, no handpick.   Overall I'm very happy, the stock definately shows some wear, but with a little more TLC I think I can get it pretty nice.  There was a little rust on the barrel bands but nothing major.  I haven't shot it yet and I'm already in love with K-31's.  I'm going to order another one from AIM next week and go for the walnut stock and handpick and see if there is a major difference in the two guns.  

Spend the money on a walnut stock if you like walnut. The beech stocks look good too so it's not necessary.
I would spend $10.00 for the sling and cap. They're nice to have, but, again, not necessary.
I would not spend the money for handpick. It's only $10.00, but all they do is grab the top 5, pick the best and ship it. It's not a real handpick where they look for the best they have.
If you want to be sure what you get buy from Allan's Armory. He usually has the best condition, but the real reason to buy from him is his descriptions are very good, and the condition is usually better than described. You won't pay a handpick fee and get one with a chewed up stock.
A lot of the buttstocks are chewed up. It comes from drills in the snow, and hobnailed boots. The stock can almost always be sanded to look good. The bluing may be worn away, but the bores are always great. The Swiss never used corrosive ammo and were fanatics about cleaning the rifle.
Jim

I'm going to go ahead and get the walnut stocked one from AIM today, with 60 rounds of the 7.5 swiss and a brick of the Aguila primer powered .22's for my starling killer.

i bought one from aim when they were $79 + $10 for the walnut and got a really nice piece. my last 3 were all from allan and he's a great guy. he messed up on the description on one of them and gave me 50% off. he will make sure the customer is happy and thats a fact.

Mine is scheduled to be delivered on Monday.   I got the walnut stock and the cap and sling.  Didn't go for the handpick since I'm going to refinish the stock and reblue it over the next couple weeks.  I'll post before and after when I'm done.  I only saw 3 K31's at Allen's available at the same price as AIM's.  Depending on the condition of AIMS and how well I can restore it, I'll probably pick up 2-3 more in a month to give me something to do this winter.  

Nothing will be as fun sitting around drinking beer, cleaning my K31, and watching the Chiefs kicking Denver's ass.  I'm checking the UPS tracking number every now and then.  Still in transit.  I hold my C&R at my parents since I'm there while my house is being remodeled.  My mom can barely cart all my rifles in.  Should have seen her trying to move a 440rd brick of 7.62x54r...