Hi,
I dont know what u call it but i wanna change those RPM numbers stickers thingies as i did a Si to vtec conversion and i wanna put the correct one there.

how do i open the glass to change em ??

This is not the pic but i mean something like this :

 

I would have someone thats done it do it for you, the needles can be tricky!!! especially if they dont go on correct!

 

those are called reverse indigloo gauges...Some people say you can slip them over the needles, but others say you'll have to take the needles out completely to put those in, so whichever works best for you