Need Help Finding The Correct Rom For My PRO

[semsem1969]

Hello to everyone,
am new in here and i like this forum its quit nice . also am new to the whole thing about flashing Rom and updating the phone and please i need your help please.
i have a touch pro its from Softbank Carrier (JAPAN) its call X05HT model and i need to change the os from Japanese to English .
so i assume that the phone or what they using is cdma type (UMTS 3G 2100) and to be sure how i could find out ???
second is do i have to sim unlock or no need before i start?
and what files do i need and what the best Rom to suite my phone.
i can not choose cause am a beginner and i dont know what is ok and what is not.
finally if you can explain to me what is disadvantage of upgrading to a different rom (example am not gonna be able to use messages or internet ...etc...)
i know i asked too much but really i appreciate it .
thanks