...When you said 1 screw in the handle holds the power supply. Did you men the screw on the outside of the handle...
No, Jim meant there's one screw that holds the power supply to the floor.
There's another screw on the left side of the power supply box that secures the cover.
You have to get that off to undo yet another screw that holds the power supply to the cabinet wall...

Once you get all those off, you can pull out the power supply box.
As for the slot handle, there's a hex bolt in the very bottom of the handle.
It's easier to get at if you remove the topbox glass first, and gently lay down the cabinet onto it's left side.
Takeout the heavy stuff first like the coin hopper and the power supply...the machine will be much lighter to lay down.
Now, look at the bottom of the handle, there's a hole, in there is a hex bolt that you need to use the correct sized Allen key in order to remove that and the washer.
Once removed, you can wiggle/work the handle out of the shaft, and then you can pop off the IGT logo cover hub.
Inside the cabinet in the handle mechanism are 3 nuts that secure the handle that you can remove with a socket wrench.
Offhand I think they're either 7/16" or 1/2" nuts?
You can find out in which holes they are and approx. where they're located, by judging the bolts surrounding the shaft on the outside of the cabinet.
The top 2 nuts are sort of easy to remove, it's that bottom nut where you have to sort of wiggle the socket around the springs to get the socket onto the nut...you'll see....use a socket extension to help work the socket around the springs with some leverage.
You first need to undo the wiring connectors at top, for the handle release solenoid, and also the two wires located lower - for the handle microswitch.
You don't want to rip those apart when the handle mech comes off the wall.
Take your time...this is a hobby, not a job...lol