My first advice is to accept Jill’s offer for real-time help. Wow, thank you, Jill!
Second, it does not sound like your problems are specific to AR Sandbox and you might be able to find a local Linux expert (i.e. a colleage, a student technology club, etc.) that can visit your sandbox and quickly fix it.
There will be some differences between Ubuntu (used by System76) and Mint (used by UC Davis). Are you using the instructions from UC Davis or from System76?