Bruce, When I started collecting, I took my newly purchased Winchesters and immediately disassembled and cleaned them. Some of those guns needed it and others didn’t. I found myself turning screws that had never been turned since they left the factory, removing wood that was sealed to the metal, and all the visually evidence that the gun was honest. I have long since regretted down grading these pieces of history. If someone has been there before you, ok, but you don’t want to be the first to remove the proof of age. T/R

Bruce, congrats on your first Winchester.  May there be many more. 

As for cleaning, I kind of followed the same path as TR in taking apart and cleaning these guns when I first started collecting and have come to regret doing so as the years past for the same reason he stated.  As TR and Tedk mentioned, if youve got a discerning eye, you can tell the ones that have been taken apart and when one hasnt.  That said, the one thing that did benefit me down the road in understanding each of the models was taking them apart, studying its parts and how they interact and then reassembling.  Having that experience was helpful in understand functional issues that seldomly occur.  Really, just wipe down the outside, light lube in the receiver, and keep the bore clean and you should be good. 

Chris