Ken, In my opinion 2500. is a very reasonable estimate for unstepping, stripping, preparing, painting, reassembling, restepping and retuning the rig.
You would be well advised to take lots of pics or even video the mast and fittings before the disassembly starts wether you have it done by the yard or do it yourself.
While the rig is down consider everything else you might want to do. Such as tri-color light, new wiring, antenna, lightning dissapter, conduit if you don''t have it now, etc. etc. Any mast work goes easier and faster when it''s laying on horses.
Make sure that the threads of any fasteners that are added after the paint job are coated with an insulating material to prevent corrosion.
Bottom line: this is a big job and you should be prepared to be involved every step of the way no matter who does the actual work. Good luck