Assistance needed choosing new derailleur

sunnytour Posts: 15
edited September 2016 in MTB beginners
Hi guys,

I have a 2002 Scott Voltage MX5, a basic bike with basic Shimano Tourney eqiupment. Now, I would like to upgrade rear derailleur with the one from Alivio or Deore group set. I was wondering if any 7-gear derailleur would fit to my bike and are there any other parts that would have to be replaced, such as rear shifter.

I would appreciate any help,