if im gonna replace one shift solenoid in my 99 4x4 am i better off to just replace them all?

 

If you have the money. It will cut down on having to drop the pan again if another one fails. Before you put in the solenoids though, test the resistance on the new ones. I believe the spec is 20-30 Ohms resistance. Also, make absolutely sure that you do not damage the wiring harness when you put the pan back on.

Why are you replacing the solenoid?

 

Cause i had the codes pulled an my b solenoid was coming up stuck open.

 

The reason I ask is because the code might not mean that the solenoid itself is at fault.

It sounds like your code was P0757, but have a look at the link below for some diagnostic tips:
P0756 - Shift Solenoid B Performance or Stuck Off