Hi crack3dmach1n3. Welcome to the forums.
Yeah, that is a bit ambitious. But anyhow, it's good that you've forgotten what you learned in the 90s, as it would only be a chain around your ankles now, as things have moved on.
If you have plenty of time, you can learn how to do all of this via books (such as SitePoint books), online courses etc. But it's learning a whole new, multi-faceted discipline, and it takes time. My advice would be to hire someone to do this, but it's up to you.
As for hosting costs, yes, if your users are downloading a lot of content, you will need to pay extra for the bandwidth being used. A good option to consider here is to use a separate hosting service for the videos content, often called a CDN (content delivery network) which is optimized for serving up large files quickly and offers cheaper storage. So, the videos would display on your site, but they would be pulled in from an external source (not that the user would know). It's like when you watch a YouTube video on someone's site. It's actually being fed to the page from YouTube.