In that condition with those grips I would think it's a $500 gun. If you do the math backwards it's really about a $400 gun but i'm sure someone that wants a woods carry/hunting .44 Magnum would go $500.
When you reblue a gun is no longer has ANY original finish left which kills value. A reblue wont increase the value if thats your goal. You could get $475-500 for that gun as is, or spend $200 on. Reblue and get $500-550 for it. You would be further ahead to sell it, add $100 to what you get and buy a nicer one for $600
We would not reblue here but not because of value as much as you have a model 29 with honest wear on it from it being used and shot as intended. Re blue and yes you have a great looking revolver but then may be hesitate to shoot and use it because it is going to have wear on it when you carry, shoot, have it outside, etc and if you do that a lot it may end up looking the same as it does now. Much like a new car you drive it and it gets dirt, dings, scraps but most will likely not repaint the car, they will just continue driving and enjoying it as it is.