Upgrading a W610i?

Hello! As a new member, i am not sure that this even is the correct place to ask this!

I have a SE W610i, and im going to give it to my gf in a week! But i want it to be special! I would like to upgrade it, if possible. So my questions are:

1. What firmware can i upgrade it too?
2. What can i do to make it even better?
3. Are there any tweaks that i should know about?
4. Does anyone know where i can buy new covers? (ive heard about "mytrendyphone.no", but they doesent have the cover i want. (I want it all black!)
5. I Think i read about it being possible to switch covers between k550 and w610, is that correct? If so, is there something that i should need to know before i do that?
6. If its no possible to change covers between k550 and w610, is it possible to change the keypad light from orange to blue? I think the black cover/blue light would be awesome :D

Please! Help me :D And if i have posted this wrong, please move it :D

Best regards
Opius :a013