One-off WordPress update and personalised update guide

I co-own a WordPress blog at www.merchantandmakers.com. I need a one-off job that includes:
1. Updatng WordPress core, all plugins and themes
2. Testing the site afterwards to ensure nothing is broken
3. Creating a very intuitive, clear step-by-step written guide with screenshots for me to follow in the future that explains:
a) how to backup my site
b) How to update WordPress, plugins, and themes
c) What to check to make sure the site still works
The guide should be easy enough to follow for a non-technical user to follow. Please confirm you've done this kind of handover before.
My budget is around £150. Ideally this should be done within 2-3 hours.