Im going to be running a linode server 2GB version how do I connect the sandstorm.io GUI to the linode server? do I have to have sandstorm I just want to have an email server maybe music play ect.
If you just want to run an email server and sandstorm then it's pretty simple. Go to iRedMail, follow the installation instructions, then simply follow the installation instructions for Sandstorm. Sandstorm uses docker, which takes more configuration but since your not running any web servers this is relatively simple (ports won't conflict). Follow wendells video, if you get lost.
what linux distro should I run in my linode server?
Ubuntu 14.04 works pretty well with sandstorm, I'm not sure about the email though.
I personally use debian, it works, plus it's more stable than ubuntu. If you want bleeding edge though, go with ubuntu, the LTS versions.
if I want iredmail do I have to pay for sandstorm.io?
Have a look at the requirements for both, I use the 2 core 4GB version for my linode server, but I'm running discourse and other servers instances on it.
The only thing that iRedMail uses the most resources for is clamav, if you wanted to you could just disable/not install it. However I would advise not too.
Think about what your going to use sandstorm for, if it's minimal then go for the free version of them hosting it, I only use mine for spreadsheets.