Bumper Repair

I own a 1996 BMW 318i convertible and a little while ago my sister ran over a traffic cone on the highway. Because this car is so low to the ground, it completely ripped off half the front bumper on the passenger side, as well as both of the fog lights and the bottom of the bumper on the drivers side. I've been putting off repairing the damage because I know it will be pricey due to the fact I need to probably replace the whole thing. My question is if I buy the bumper online, will it really make a difference in the cost of the repair at a body shop? And if I do decide to order one, do I need to get any other parts beside the bumper itself, i.E. Brackets, lights, molding or anything? K, sorry I know this is long, but one more question, I need to replace the tires on this car as well, and I'm not a big car person and I'm wondering if there are any you can recommend and any I should steer clear of. Thank you so much!