Does any know of any examples out there that show how to implement ISearchService using Azure search service in Sitefinity?
Sitefinity supports Azure search out of the box. And you don't need to implement your own ISearchService.
This is official documentation how to connect your Sitefintiy to Azure search service: https://www.progress.com/documentation/sitefinity-cms/generate-and-store-search-indexes-in-the-cloud