Andy, It’s detailed in I need help choosing a beginner's chromatic harmonica (Easttop Forerunner 1.0) - #7 by Jay1. A few words of warning, some you may already know: (a) when removing the mouthpiece and slide there are two small clear plastic buffers on the screws, try not to drop them but if they are lost similar plastic tube can be obtained from fishing tackle shops; (b) the mouthpiece screws are in my view too short and can easily be damaged at the ends, treat them with care, I’m trying to locate suitable longer screws: (c) be careful with the slide spring it can fly 
I hold mine with long nose pliers when removing/refitting it.
I’ve quite a case listing over the next few weeks including some overseas so might not be able to do much on the forum. Jay1
1 Like