Help: Organising Model UN

I've always wanted to do Model UN but its not really a thing in my area. I'm on school council and have gotten SLT to agree to run it if i can create a plan for how to organise all the aspects including the training plan. Coming from a low income area with a lot of talented young people who wont have much going for them when the time comes for writing sixth form or uni applications- since academic extracurriculars are rare in my school and expensive to do externally- it would be amazing if i could get this up and running asap. So it would be amazing if i could turn it into an annual or even biannual event and have the next gen of club executives/ leaders (since i'm starting year 11 in September) secured by the end of the academic year. I know it's usually done on a much larger scale but i think it would only be possible to organon within my school at the moment.
Has anyone ever done/ run a Model UN club or event before? Any advice or resources would be greatly appreciated.
I'm prepared to put in a lot of work.

Hiya, this sounds like a wonderful plan! My school does Model UN but I'm not hugely involved. Ours mostly works with other local schools in my area, so I'm not sure how helpful I'll be, but I'll give my two cents anyway!
You likely already know, but the UN has a 'Set up your own Model UN' page here: https://www.un.org/en/mun/model-un-guide
and there are also some school resources here: https://una.org.uk/sites/default/files/Miscellaneous/School%20resources.pdf
Do you have any teachers helping/working alongside you? It would be beneficial to link your MUN to a department eg Geography or Politics, and they might be able to assist you a little more directly than I can!
This might also help: https://mun.bestdelegate.com/wp-content/uploads/2018/11/Diplomat-Guide-2019.pdf
You should probably start by gauging interest, and putting together a list of countries for your fellow students to research. Having it set up like a MUN practice club to start may work best, as your schoolmates' understanding of MUN may be shaky at first. Gradually making it bigger to a full day, then meeting with other schools, then moving on to larger competitions should be a way to convince your SLT it should stay!
I'm going to assume you had to 'pitch' the MUN idea to your SLT, so you probably have a basic plan already? You could adapt this into a PowerPoint to send around to your countries/students to make sure they're all on the same page.
Please let me know if there's anything I've not explained very well or anything else I could help with, I wish you the very best of luck in setting this up!