Have trial 2014 almost expired but would like to try 2015 version

I am finally learning Sketchup and I have a couple of hours left on my trial 2014 Pro version but want to try and will most likely purchase Pro 2015. Do I uninstall 2014 and then install 2015, or go for the upgrade even though I have not yet purchased 2014? If I go the upgrade route, do I get to try 2015 before purchasing it? Thanks.

Multiple releases of SketchUp can coexist - you don’t need to uninstall 2014 to install 2015. And 2015 comes with a Pro trial period just as in the past.