Well, it shows a good bit of honest wear and finish loss but if the corrosion isn't too deep it can be brought back a bit closer to its original condition. Probably the first place to start is with a good detail cleaning to assess the situation. That will give you a better idea of what you are working with and what is possible.
How well versed are you in the assembly/disassembly of S&W revolvers? Do you have the tools necessary to do the job? You can clean up the outside by removing the grips and using fine steel wool ( # 0000 ) and a detail brush like an old tooth brush. Any decent penetrating oil will remove a fair amount of the surface rust and general crud when applied with the steel wool and brush but these are methods primarily for the outside of the gun. To clean the barrel and the chambers you will need properly sized gun cleaning tools. If you don't already have them I would suggest picking up some if you intend to do this job properly. Barring that, I have used Q-Tips, old 100% cotton rags and things as mundane as chopsticks from carry out Chinese food in a pinch. Not ideal but effective enough if used with patience.
If the gun is to be restored to full function it will probably need to make a trip to a revolver smith at some point to have the internal parts checked out and cleaned or replaced as necessary. At that point it will have the sear engagement and the timing checked for safe operation and probably an assessment of whether it is feasible to do a complete restoration.
Hope this was helpful as a place to start.
