Hi,
Simplest is probably to use the Grafana docker image tagged master if that’s possible for you. Otherwise install one of the Grafana nightly builds.
I understand that you want to try it out with data from your existing installation. I recommend that you backup your database and restore a copy to be used for Grafana v5. However, if you make changes to both old installation database and v5 database, don’t expect to be able to merge the two databases together at a later point.
Above answer are solely based on that I understand you only want to try out Grafana 5.0. Just so you understand, we have a lot of people running Grafana nightly builds in production and updating whenever new nightly builds are released. It’s a question of what you prefer, living on the edge or not 
Please let me know if this answers your questions
Marcus