you can find sks rifle at virtually any gun shop but searching for a Chinese version may be a little more difficult.
Is it marked with Chinese characters or in the Cyrilic alphabet? <><><> As above. In addition, MOST Russian SKS rifles had blade style bayonets. MOST Chinese rifle had a spike type bayonet. But marlings are the defintive answer.
No. ALL SKS rifles - Soviet, Chinese, Albanian, Yugoslav, Chinese, Romanian, N. Korean, N. Vietnamese and East German - are chambered for the 7.62x39 M1943 cartridge, and can facilitate only that cartridge.
In the vicinity of $200 for a basic Type 56 carbine, up to $500 - $600 for some of the more 'exotic' models, like the paratrooper carbine, and detachable magazine SKS D and SKS M rifles.
You should be able to find plenty on Google Images, Bing, Flickr/Flickrivr, etc. The Chinese models are either the Type 56 Carbine, or you can search for "SKS-M" or "SKS-D" if you're looking for the models which use a detachable AK magazine.
The Kalashnikov AK47 and the SKS rifles, 82mm Chinese mortars, 120mm Soviet Rockets.
Depends on country of origin, and which part of the country you're in. I've seen laminate stock Soviet SKS rifles go for well over $400. I've seen the same for unissued condition Yugoslav M59/66 rifles. You might be able to find a basic Chinese Type 56 carbine for $200 - $250 or an issued condition M59/66 for about the same. However, some Chinese models command a premium for their rarity - particularly the paratrooper carbines, and detachable magazine SKS-M and SKS-D rifles, which can cost into the $500 range. The Albanian SKS is pretty rare, and might for anywhere from $300 - $450. The most expensive ones will be the ultra rare Vietnamese, East German, and North Korean variants, which typically command prices upwards of $1000 whenever someone who has one decides to sell it.
Very similar, minor differences,
Literally, millions. There were made by Russia, China, and many of the Soviet allies. While more AK47s have been made, there are a LOT of SKS rifles out there. No exact number are available.
Some SKS rifles were brought back... most of them were manufactured in East Germany or China, as the Vietnamese made SKS rifles were and are extremely rare. They were either captured or sold/traded for favours to other soldiers in-country.
They began production of the Type 56 carbine (the Chinese designation for the SKS) in 1956, and production (for the civil market) continues to the present day.
The only SKS carbines currently which require registration are the Chinese-made SKS-M and SKS-D models. Those could not be imported into the state after 1989, and had to be registered by 2000.
Seems to work well for all firearms.