Just found a VRX that's being parted out. Gearbox and shifter mechanism are going for about $250, wondering whats involved with putting a 5 speed in to give my car some more oomph since I mostly drive it around town. Do I need anything other than the gearbox and shifting mechanism? Any issues with the ECU etc?

I'm assuming you're going a 5 speed auto....

Not 100% sure exactly what you'd need for a KF but when doing a 4 speed auto to 5 speed auto in a KJ/TJ off the top of my head you'll need the following.

gearbox
gearbox mount
engine loom
ecu, bem, key barrel, keys, door and boot locks (if you want to keep the immobilser function)
shifter assembly
intermediate shaft
passenger driveshaft (99% sure it's the passenger shaft you'll need but could be the drivers side).

Being a KF you may also need to swap some dash looms as well but not sure. At least you have a bit of an idea now as to what is needed.

That ends that idea then