Depnding on the year of the car he can either do it himself or have to bring it to the dealer to change it with there computer. I have a 96 740i and the only way for me is through the dealer. I believe if it is 95> prior he can go into the OBC and change it. You know how there's 2 buttons on your dash cluster?
LEFT AND RIGHT?
For all practical purposes, let's just call them "L & R"
1) Press and hold "R" down for 5-6 seconds
2) You'll see TEST NR 01 or something like that
3) PRESS QUICKLY "L"
4) You'll see your vin ID, mine is DH04759
5) ADD THE DIGITS :: 4 + 7 + 5 + 9 = 25
6) now now now.... the EASY part
7) press "R" again until you reach TEST NR 19
8) Press "L" to select
9) You'l see "LOCK: ON"
10) Press "L" until you reach "25" (the # THAT WAS THE RESULT OF YOUR ADDITION!!!!!!!!! COULD BE ANY NUMBER FROM 0-45)
11) AFTER you have the correct # there, BRIEFLY press the "R" button
12) Display will revert to TEST NR 01
13) COMPUTER IS UNLOCKED
14) To test, press "R" repeatedly to go to TEST NR 7 (TEMP and RPM)
15) When you reach TEST NR 7 press "L" --
16) Press "L" to toggle between RPM and TEMP
Once it's unlocked you can scroll through and find Language. And should be able to scroll through the different languages.
Try this site
www.e38.org