I'm with namloot on the motor height issue. If it's an AK, remove the outer grip, and you can adjust the motor height.
As far as internals, I'd say it wouldn't be a bad idea to upgrade the internals. However, if you don't want to spend a fortune on internals, you could get away with just cleaning out the mechbox of the thick goop these guns are usually lubed with, replacing the stock plastic bushings with metal ones, reshim the gears (bushings & shims will cost less than $25), and relubricate with proper gear grease or white lithium grease (from Cdn Tire). This alone would make it shoot more consistently and make it more reliable.
As far as other internals, I'd say that all the internals in that gun will be rather cheap, so any upgraded parts would be an improvement. Personally, I'd get parts other than TM, as most aftermarket parts are of better quality anyway. But seriously, if the gun shoots well with the stock parts, you're probably better to just leave the rest of the internals stock and just wait till something breaks to repair it.
As for how easy it is to do, that's another story. Once you know what you're doing and understand how everything works, the process is not horribly complicated. You can go to
www.mechbox.com and watch their videos on how to disassemble and reassemble your guns. They have video guides on how to disassemble and reassemble a TM-compatible AK, as well as a V3 mechbox upgrade video guide. You may want took through them several times each before actually attempting the work. However, as you probably know, the 'ideal situation' in these videos and reality often differ, especially when you consider your gun is one of the cheaper Chinese clones, which are generally TM compatible, but not always 100%.