Not challenging at all; I buy and sell guns quite often, and the first thing I do when I buy a gun is to disassemble it. Inserting a magazine into a gun and pulling the tigger as part of reassembly is strange at best, and dangerous at worst. Of course, now I will be told it's dangerous if you are stupid enough to leave a round in the magazine. Which, of course, isn't the point. I have very little problems with safety devices (e.g. the S&W internal locks on their revolvers do not concern me in the least, but many hate it).
I do not understand the strong following of the pistol. I don't mean I don't understand why people like the pistol--I understand that. But the gun is just a decent plinker, with some advantages and some disadvantages. There are five to ten other target pistols in the market that are comparable, yet none have the type of fanboyism that the Ruger produces (well, maybe the S&W model 41 crowd).
This post is not an invitation to convince me that the ruger deserves all the praise the fanboys heap upon it. I am familiar with the weapon, and I dislike it for a number of reasons, and respect it for a number of other reasons.
I will say that if you did disassemble the Single Ten, it is much more difficult than the Mark 3 IMO. But there is very little need to disassemble the revolver--I doubt one out of every ten single six/ten owners have disassembled their revolvers.