Hm, in case of module, that I'm 10000% sure was original, IR filter was on top of sensor, protected by *mold* plastic case. It;s just like that You need to break this plastic all-together, to remove filter. Quite low chances of not scratching sensor matrix :/

Also, there is another caveat - ultra-thin copper wire, than connects base PCB (with sensor) to copper ring. It's super-easy to break it, while un-glueing base of module. Not to mention that - at least in my case - this glue was stronger than plastic itself, i.e. parts of plastic break more easily than parts of glue holding them together... 0_o
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Also, I'm quite surprised, by how Your module looks, externally (from photos). It's totally different from what I've removed from genuine N900 - I'll post photos later.

/Estel