Roof rack is very easy to install. Anyone can do it. No electric wiring involved.
Get a torque screw driver if possible.
As for autodimming mirror, I installed it myself. Some complexity involved depending on your luck. With backview camera, it gets even more involved. As a DIYer, you must enjoy doing it. If not, my advice is pay to have Mazda dealer install it for you.
Warranty? The law says that unless the accessories installed directly affect the failed parts that need repair, the fact that you installed that thing will not void the warranty of the failed parts. That is the Mag.-Moss Act.
However, if you created a short somewhere while installing stuff, the arguments could get complicated if some electronics got affected. The risk is always there if you DIY.