Change of Wordpress domain

General information for the website: Endurance Coaching and swim/run technical coaching
Kind of development: Customization of existing website
Description of every page/module: The website is fully functioning, though needs improvement - as most websites do! Current pages are fine
Description of requirements/features: Currently, the only requirement I have - the reason for posting this job - is removing the wordpress subdomain from the web URLs. I was very fortunate that a friend built the website for me, however he didn't remove the subdomain and now it appears to be causing issues in various different SEO ways.

The brief for this job is to remove the subdomain from the whole site - and to relink all the pages to the new URLs if possible.
Extra services needed: Domain
Specific technologies required: None required
Similar urls: www.tri-coaching.co.uk/wordpress
Extra notes: Any other suggestions you would make as you go through the site, I'd be more than open to then contract you to make extra changes after this.