i have to replace a key blade on a key, i have the new blade but i have to open the key itself to transfer the blade, i would'nt want to damage the key... how does that thing open ??

 

Funny, I just did this with my key.

Under the loop where the key ring goes, there is a little slot where you can pop the key open.
Once you get it apart, there will be a small roll pin holding the key blade to the plastic, I threaded a small self-tapping screw into the roll pin and pulled it out with some pliers.
You may or may not have to swap the transponder too.

 

What year MINI? The keys are different!!!

 

05, newer key style

 

I was just about to edit my post, I have the early key that does not charge itself while in the ignition.

EDIT: I don't think the later key comes apart, but I could be wrong.

 

i know they come apart, i bought a new blade for it, but can't manage to open it.