Hi, new here but am working on getting my bicycle road ready and hoping for some information. I have a Schwinn Landmark bicycle which has a Shimano 7 speed deraileur system. When I pulled the rear wheel off I discovered that the rear axle is bent pretty badly. What do I need to know in order to order a replacement and will I need special tools to replace it? I would obviously like to upgrade to a better material while I'm at it. The bicycle is almost new but I'm a big guy so I need to beef this up somehow. Thanks!