I am a freelance WordPress developer who creates custom theme and plugins for clients. Additionally I am using WordPress to build a series of platform and tools for small businesses and startups. I am originally form the UK (native English speaker), but now live in Finland.
Adding the custom code (assuming that the code is well written and doesn't contain any errors) to a child theme page template, should indeed take less than an hour. Depending on the code and the function of it, there are a number ways we can do.
1. If you have a child theme installed (I can set this up for you if you don't), we can create a page in WordPress and create a page template for that slug. This means that you can never change the url of the page in question.
2. If the code is compatible, we can create a plugin that injects the code into the page using a shortcode. This means that the code shortcode isn't part of your theme - good if you want to change theme at anypoint. It also means that you can insert the code on any page that you choose.
For both of these options, I would need access to your WordPress installation and your webhost to upload files. The only upset or potential problem I can see is if there are errors in the code that you want uploading.
I look forward to hearing form you.