At that amount of use I would recommend replacing the housing as well as the cable...Both cable and housing are the same for SRAM and Shimano...

Cables are, 1.6mm for brakes, 1.1mm or 1.2mm for shifters. The cables have different ends so that helps to figure out which is which.

Housing is 5mm for brakes and 4mm or 5mm for shifters. Again, there is brake housing and shifter housing, they are not interchangeable. For the shifter housing you can use either the 4mm or 5mm, but for some bikes with internal cable routing the cable stops are designed for 4mm only. I'd say to replace the housing with the same size housing you currently have.