well if your paying lots for a tech to fix your gun, the worst that could happen if you break it yourself you gotta buy new parts with the money you saved by doing the work yourself.
if your fairly mechanically inclined i say do it your self using online resources, like he said mechbox.com is handy.
i've installed helical gears in my gun myself as one of my first times opening the gun and i'm happy to say it still works great, last time i opened the gearbox the gears weren't stipped. been running them over a year now. just to prove it can be done is my point.
be careful with the screws, when you take them out, find a system for yourself to remember where they go when you put them back in. i put them down in roughtly a gearbox arrangement so it looks the same going back in.
and if it will help take pictures before you take any part out.
i found however if i tighten the screws too much in my gearbox it resticts the spinning of the gears, so don't over tighten. those screws are little, don't need much torque. if your worried use some thead lock.
and after shiming test your gears by not putting in the piston or spring, they should spin freely by finger.