simple question... In visual studio, how would i programmatically set my custom xslt to the search results webpart?
Are you creating your own version of the CSRWP? Or are you customizing a webpart on an existing page?
For both cases, you have to modify the ItemXslLink, and set it to the link to your xslt.
If it's the second case, you can use the SPWeb.GetLimitedWebPartManager to change the properties of a webpart on an existing page.