I had a similar issue where Install.sh wouldnt do anything and gave me some odd error. I got around this by opening the Install.sh file and copying the command (something like "sudo apt-get filename filename filename mono" ) into the terminal (terminal was opened inside the game folder, I am not sure if this matters). However I had to remove the word "mono" at the end of the command, and install that seperatly by following this
http://www.mono-project.com/download/#download-lin (I installed both "mono-devel" and "mono-complete" for no particular reason and am not sure which one is the correct one).
My issue wasnt exactly the same as what you describe and I was installing it onto a chromebook (with linux) so this might not do it for you.
Edit: I reread your question and saw you are using Mint, I dont know anything about Mint so sorry if what I said isnt relevant