Hello Grumpy_Tyrant haven't seen you in a while, glad to see you back.
The glue that holds that plate is not permanent and the plate should be easily popped off. You don't need to replace the plate after your repairs. I don't currently have an extra 2 speed motor in my repair parts box to show you pictures. For all the youngsters out there do not attempt this without the help of a parent or adult. What I use is a thinner pocketknife blade to get under that plate and try to pop it up. Move around the plate until it comes off. Sometimes there will be a stubborn part and the plate will break but as long as it is no longer covering the seam down the middle of the housing you will be alright. Once you get that top plate off you can open the housing by opening the top and front clip. Be careful here because there is a spring and you don't want to spill out the gears until you know their orientation inside the housing. Taking a closeup picture of the inside will help you put them back into the right place when reassembling. While I have a motor open I like to lubricate the gears and their shafts using a little lithium white grease for gears generally used trains and remote controlled cars. That Yufuin No Mori is a fine train, let us know how it goes.
The glue that holds that plate is not permanent and the plate should be easily popped off. You don't need to replace the plate after your repairs. I don't currently have an extra 2 speed motor in my repair parts box to show you pictures. For all the youngsters out there do not attempt this without the help of a parent or adult. What I use is a thinner pocketknife blade to get under that plate and try to pop it up. Move around the plate until it comes off. Sometimes there will be a stubborn part and the plate will break but as long as it is no longer covering the seam down the middle of the housing you will be alright. Once you get that top plate off you can open the housing by opening the top and front clip. Be careful here because there is a spring and you don't want to spill out the gears until you know their orientation inside the housing. Taking a closeup picture of the inside will help you put them back into the right place when reassembling. While I have a motor open I like to lubricate the gears and their shafts using a little lithium white grease for gears generally used trains and remote controlled cars. That Yufuin No Mori is a fine train, let us know how it goes.