do you have to take the car to dealership when replacing battery in BMW 3 Series how do you reset computer on your own
No, most places that sell and install batteries professionally know the protocols for battery replacement, stay away from places like Walmart, they will sell you a battery and just unhook yours, put in the replacement and then say oops when it won't start due to alarm or loss of code presets. Call a place first and make sure they have the equipment to do it right. As far as a computer reset to factory, the only true way is to completely electrically disconnect the ECM and let it sit overnight before reconnecting it, after it is reconnected you need to drive it as you normally do for at least 15 minutes, if everything is right then there should not be any warning lights.
tennisshoes is right, battery's only need programming for the 2006 and newer E90 chassis. There is a lot of misinformation out at the auto parts stores.
Search BMW 3 Series Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
BMW 3 Series Experts