How can I find an expert CiviCRM WordPress developer?
A great place to find a CiviCRM expert is on CiviCRM.org! There's a list of CiviCRM providers at https://civicrm.org/providers

You can use the filters on that page to identify a good match by (for example) services offered, CMS expertise, language and location. Here's a listing of CiviCRM / WordPress implementors.

Being an open source project, much of the work happens out in the open. Other places you can identify good people to work with are places like Stack Exchange (this site), CiviCRM chat, the CiviCRM bug tracker, and other community resources.