Opening Remote Unit Of Is200 Key

[Dizz]

As the title says I'm trying to figure out how to open up the remote buttons section of an IS200 key. I have the key itself open and have the remote section out. It's a 2 button remote and was hoping to convert it to a 3 button. I have a new 3 button casing and here is a photo of what I have:

As you can see the microswitch is visible behind clear plastic where the boot release button would be but what I can't figure out is if the whole section is glued together and if so how can I open it? Not sure if I have to cut the clear plastic if so I was thinking that I could possibly cut it in place and then cut on of the 3 button key pads to just have the button (and a bit of a surround) and push it down through??

Any help would be appreciated.

Here's a few pics of similar 2 and 3 button remotes: