Good advice from David there Watchbear but what I would say is after having a service and the watch is running fast, you will probably find that someone before you shortened the effective length of the spring to get it to keep time without breaking down the watch and servicing it, either that or one of the pallet jewels is loose and the escape wheel is tripping through the jewels where the depthing is wrong?
Dont worry about poising tools and timing screws just yet. If the watch was running that fast you were heading down the correct road, the hairspring needed to be lengthened. When this is done you then need to adjust the collet on the balance staff to get the watch back in beat. I have been messing about with hairsprings all day today on a pocket watch and a wrist watch and they can be a pain but as David suggests get a bit of practice on an old movement. Those tiny brass pins or wedges that hold the spring in place can be made if you lose one.
When you have worked out where the spring needs to be pinned you then need to make sure the roller jewel is in the correct position otherwise as you know the watch will run out of beat. Once the spring is pinned the roller jewel should be in a line with the setting lever and the centre of the escape wheel. On some watches the hairspring has to be taken off of the cock as you cant get to the collet to adjust it. Get it all where you think it should be and try it. Be patient, walk away when it gets too much and make sure you have a good fine pair of tweezers to work with. I lost 3 small brass pins today where they just flew off, I dont bother looking for them any longer, it is quicker to make a new one.
One last thing, you dont have to remove the stud to re-pin the hairspring, if anything it should help to make it easier as if you leave the stud in place as it gives the hole you need to get the spring through a steady platform. Think about how you would hold that tiny stud while trying to get the spring back through it.
Good luck and let us know how it turns out 
Paul.
