As for if the gears are worth it, and if you should have a go at the install yourself. Personally im only using a 22k RPM High torque motor which is one of the slower ones available. I would a set of upgraded gears will be a good help, esp if you use a LiPo or plan to in the future. also a new piston could be a good plan. I would suggest checking out a few guides online for pistons, as alot of people take our a tooth or 2 from the bottom of the piston to get a better Angle of engagement, but also it can be worth looking for a piston with metal teeth on the bottom as they tend to last a bit longer. As for should you have a go at doing the tech work yourself.. absoloutly, its a good thing to learn, and as you said worst case you get F&O to finish the job if your having no luck.