Yes, you can install 17 inch wheels on your 325i provided the wheels are Bona-fied BMW hub centering wheels with the correct width and offset. If you have the wheels available, it would be very wise to mount the new wheels as a trial on both the fron...
if you had a bike with 9 wheels, you wouldn't have a bike...bike is short for bicycle, and the "bi" part means 2...meaning wheels... but to answer your question, it would take longer then if you had 2 wheels, becasue you would have to apply more torq...
i ride spitfire their really good wheels you should get some spit fires