Is this a good idea for a website? Will it be hard to make?

Honestly, the idea has been more or less done before, as you mentioned. But, if you are able to implement something unique and awesome, and people find out about it, anything can happen. Depending on how much content there is, it could be a massive coding project. Do you know PHP, HTML, JavaScript, Python? If not, it could be a lot harder. Otherwise, nothing is out of the realm of possibility.