I have a 2007 Suzuki GS500 (Motorcycle) and the exhaust valve went out so how do i replace it?

If it is something that you don't want to try yourself, look around for an independent motorcycle mechanic. Still an expensive job because of the labor/hours involved, but he will be a lot cheaper than a dealership. Most good independents do better work than a lot of dealerships too. The engine will probably have to come out of the frame, which can be a chore sometimes. What caused the exhaust valve to go bad in the first place? Have the valves ever been adjusted?

I'm with Tim, what does "went out" mean? Is it leaking and has low compression on that side? That might be as simple as adjusting the valve lash. Or it may require pulling the head, removing the valve and cutting a new seat. Most exhaust valves are Stellite coated and don't wear like intake valves. And they can't be ground anyway. Or did you over-rev it, float the valves and bust the valve head off? If so, that most likely means a damaged valve seat, banged up or even a holed piston and even a twisted crankshaft. If you don't know and had a mechanic diagnose it, better ask them exactly what the problem is. Adjusting valve lash is pretty simple with a manual, everything else I mentioned is more difficult, requires specialized tools and knowing what you are doing is helpful lest you cause even more damage.

When you write “the exhaust valve went out” what do you mean? You will not be able to cost the job without investigating it and measuring; and you will not prevent these things without knowing why and how it “went out” – if it is sticking out of the engine you might as well replace the engine. You definitely need a Haynes or Clymer manual and plenty of time. Take it slow, take lots of pictures as you go and use the proper tools – especially noting the torque settings. This is not a job that you can zip through in an hour or two if you are inexperienced – if you make a mistake with the timing chain you will bugger all the valves.