I've been shooting SKS rifle for about four years now my first rifle was a refurbish all matching 1970 Yugo M59/66 I paid $149 for it,I was lucky enough to hand pick my own for a crate of 12 rifles. Thanks to another board I hang out on a lot I had a good idea what to look for at the time in a rifle but you never really know what you have till you get them stripped down,cleaned and give them a test fire.
One of the biggest problem with the Yugo rifle is that they have had a steady diet of corrosive ammo fed through them during there entire service life. This is not usually a problem as long as the rifle is cleaned and service properly,another is the gas valve and block found on the M59/66 rifles,this areas usually suffer the most from improper cleaning after using corrosive ammo as many people have found after purchasing the Yugo rifles and the valve is corroded in place or pitted,plus the extra movement can cause wear and tear around the nipple of the valve where it contacts the gas tube and cause a loss of gas pressure leading to short stroking of the bolt and FTE issues.
As far as the Yugo having a chromed lined bore goes I consider that a non issue in a rifle that was properly maintained for the beginning,even a chromed bore want save you from corrosive ammo if left unattended and there is always the entire gas system that isn't chromed lined to begin with,so there is more to consider than just the bore lining when choosing a SKS.
As far as my Yugo goes,other than some wear on the bluing and a few dents and dings in the original wood stock it's in excellent condition,I did have to replace the gas valve due to FTE and stove pipe problems with Wolf ammo,it would function perfectly with any other Russian or American ammo with the original valve I replaced it with a CNC Worriers valve and it even functions perfectly with the Wolf ammo from then on. It could have just been a bad lot of Wolf which i haven't use in my SKS rifle in over three years,it may be fine ammo but it's on the bottom of my ammo food chain. As with any rifle I own I always set up to reload for it,I don't trust cheap imported ammo to always be available and being that I have reloaded for 25+years it wasn't much of a investment in dies and tools to do the X39mm rd. anyway.
The SKS lends itself well to reloads,you just can't imagine how much more accurate the SKS is with some good hand crafted ammo that matches the rife as well as the bullet performance of American vs. Russian in target shooting and hunting. I understand this isn't for everyone so each to his own on that. All that I can say is I can cut any group in half or less with a stock SKS I own with reloads vs. any store bough ammo at any range. Although I haven't done it as of yet I'm considering th Murray's spring loaded firing pin kit $47 installed by Murray,just in case the availability of Mil-Spec primer becomes and issue and I have to switch to the softer standard LRP's which is used in American X39 ammo and can potentially cause a slam fire issue in rifles with free floating firing pins. Which I haven't had happen in three years of reloading using the Mil-Spec primer.
Other than reloads the only modification I have made to each of my SKS rifle is I replaced the front sight post with a TechSight target post $7 shipped,it's about half the dia. of the original SKS post and will give you a finer sight picture. I haven't done the trigger mod as of yet I have shot SKS rifles that have and it makes a big difference in the trigger,I just never found the triggers on my SKS rifle to be much of an issue at this point. My other SKS is a Chinese /26\ 1965 I bought NIB for $200 last year never fired,it's about 1 1/2 lb lighter than my Yugo but accuracy wise both rifles are equal. As far as modifications go sights and adjusting them properly,trigger and finally ammo that shoots consistently will make a world of difference with your SKS shooting experience. Poor maintenance and trying to make your SKS into something it's not meant to be with a lot of after market dress and your just asking for problems.