You are a wise young man. Most guys your age buy Glocks and your desire to find a proper Smith and Wesson is most commendable.
You should look for a Model 29 or a Model 29-1 or a Model 29-2.
The Model 29-3 did away with the pinned barrel and the countersunk cylinders. The Model 29-3 came out in 1982 and this was a sad day for Smith and Wesson.
The Model 29 continued and the Model 29-7 ushered in the era of MiM parts. Under no circumstances should you ever buy a Model 29-7. These are schmoed-out pieces of junk and are best used as paperweights.
If I were you, I would look for a Model 29-2 from the mid 70s. This piece would feature carbona blueing as well as Goncalo Alves stocks. I think that a Model 29-2 would probably offer you the best value.
Good luck in your hunt.
Fluffy