upgrade from 3.8153 to 4.9700 tip needed

[JCDC]

Hi guys I need your advice for my domoticz upgrade.
I have been running domoticz for some years now, and at the time I installed the bundled image for raspberry pi that was provided on a raspberry pi2. Since then I have done the upgrades successfully up to V3.8153 but when I tried to upgrade to V4.9700 domoticz wouldn't even start.
From what I have read so far I need to upgrade raspian from wheezy to stretch lite and then upgrade domoticz. I'm hesitating whether to upgrade by changing the repo or do a fresh install. If i do a fresh install and copy the domoticz folder will everything "just" work. I'm running an RFXCOM and aeotec zwaveS2 stick.
thanks for your advice and feedback.