Does anyone know how to program the LCD Display in Easy C so that you can switch between autonomous programs before a match?
Search the forums. This has been discussed pretty thoroughly. Someone else may post some links for you.
I would start by looking at the sample code in RobotC. They have a sample that is specifically tailored for code selection based on LCD input. The code takes some tweaking to put into a competition template, but it tells you how to do it in the comments section of the file.
Here are some links to some threads about LCD displays.
https://vexforum.com/t/vex-lcd-autonomous-help/27466/1&highlight=display
https://vexforum.com/t/robotc-header-file-useful-lcd-functions/21895/1
https://vexforum.com/t/how-to-program-lcd-display-robotc/24470/1
https://vexforum.com/t/question-about-lcd-display-in-robotc/27342/1