Plugin that pulls data from another site

Hello all, I am very new to the plugin game. I am a very experienced PHP coder. I have been reading the documents but nothing seems to address the problem I am having.

Basically, I want to put this site into a Plugin:
http://engine.leaguestatbook.com/marquee.php

I run a website where we take stats for leagues. What would be the best way to get that little page as a plugin? Everything I tried seemed to have errors.

Ideally, all I would want the user to do is tell the plugin what LeagueId they are assigned and then it will display the output for their league.

I have it hard coded right now to pull for only one league. Please advise on where to start.