There are a couple things:
1. Re-valve is just that they change out the "valving" inside of the shock to make it more specific to the rider (weight, style, terrain, etc).
2. Many shops do not change out anything, but rather replace fluid and do a once over on the seals, etc to make sure they will function as designed.
What specifically do you want from the shocks? Stiffer? Softer? more rebound?
Less?
If your shock guy knows what he is doing I would be asking him the questions you are asking on here. See what he says.
I just suggested Carls because everything I read they seem to really have the WE's nailed down.