Upgrading from 4 to 5

Hi Ive been trying to upgrade from unity 4 to 5 but Ive had a lot of issues. Do you have to uninstall unity 4 then get unity 5 if so how to I save game files or do you simple upgrade from 4 using 4 if so how do you do this Ive been looking for a upgrade but unity says theres no more upgrades past unity 4.something.

Many thanks Rowen.