how do I ask for a different route as the one showing up will take me in to ...
The Guru Take
All you need to do is ask!
You are allowed to change your destination as well as your route at any point. The price will be reflected according to your changes, based on duration and distance (like a regular taxi). Note that such change will impact the guranteed pricing, i.e. initially quoted fare.
To make changes, you can adjust the desteination on the Uber app OR directly instruct the driver. Easy-peasy.