Trying to take the apex 4100i apart to move

Try the calibration procedure found in the troubleshooting section of your manual first. Here are the basic instructions.
With the key in the console, press one of the Incline buttons. While the incline is changing (or the numbers on the console) , remove the key. After a few seconds, re-insert the key. The treadmill will automatically rise to the maximum incline level and then return to the minimum level. This will recalibrate the incline.
If it still doesn't move, remove the cover. Find the incline motor. You will see a slot in the end of the motor. Using a drill with a standard slotted screwdriver bit, spin the motor counterclockwise (if it is having difficulties spinning, turn clockwise instead) for just a couple seconds. Now do the calibration procedure again.
I have had machines that got stuck before. Once released and recalibrated, the operation was OK.
The service number for your machine is found on the model number sticker on the frame of the treadmill.

Sorry to inform you, that part is no longer available from the manufacturer.

You can try and do a re-calibration on the treadmill (Its listed in the Users Manual) but it sounds like the console has gone bad. To repair this you would have to replace the entire console.

hold down stop and speed + then put safety key on
hit stop once
push incline+
let it go up and down
take key off and reattach
try
if it still doesn't go the incline motor is bad

If the console lights up but the buttons don't work, then unfortunately it's probably the console and they're not repairable that I know of. You may want to check the wiring harness and the connections at the console and at the controller under the motor hood. Pull them apart and check for bent pins. If they look good, the console is most likely bad.

You need to have the power supply board rebuilt with larger Caps and resistors. Look on the internet under treadmill repairs. The board is easy to replace yourself so don't have someone come in and overcharge you. I think about 4 screws and two plugs.

try caibrating it.

Go to Nordiactrac.com and enter your Model number from the sticker on the frame. It should read NTL or NTTL then 4 or 5 number. Folow the instructions and ask for the Part's List. You should be able to find it there.

Try this calibration procedure.
Turn the power switch on. Remove the safety key. Hold the Stop and Speed Up or Speed Plus buttons down then insert the safety key.
The display should show some numbers.
Press the stop key one time and the display should show some other numbers and some 00's. Press the Incline Up button and see if the Incline begins to move, if it does let it go all the way up and then all the way down, wait a few seconds after it stops, then hit the stop key 4 times. It should be calibrated. If it didn't move then the board or the incline motor is bad.

lease send your model number and manufacturer.  Most Large format machines break down to some degree but will still be heavy buly parts.