Your system seems to be one of the original Alienware 17 (R1), which means that upgrading your GPU is possible, as it is on an MXM module. You can see your various upgrade options here: https://eurocom.com/ec/upgrade(2,263,0)Alienware_17. However, from what you describe, you may be able to solve it simply by uprading your GPU drivers, which you can do here: https://www.amd.com/en/support/graphics/amd-radeon-r9-series/amd-radeon-r9-200-series/amd-radeon-r9-m290x. When you install these, do not do a clean install, and install right over the top of your current drivers. There is a custom module that is needed by yoru system to enable graphics switching, if you install these drivers clean, you will lose the abilitiy to switch between your GPUs. Good luck!