Yes, you can replace the key with a switch/button combination. The key is mainly there as a anti-theft feature.
The kill switch is typically the ignition key. Depending on the mower it could also be a red push button labelled "emergency stop"
The STX-38 should have an electric clutch for the mower deck. The switch to engage it is on the right rear fender. It is a toggle switch. You will have to pull up on the switch and forward to engage the blades.
The engine kill switch is under the seat.
The safety switch to start the motor on a Ranchking riding mower is located in the ignition. If the clutch needs to be depressed several times before the mower will start, there might be a problem with the adjustment of the clutch.
no
This is usually caused by a faulty seat safety switch.
Like any power switch you have Power in, Ground, Switched Power out and the Switch Terminal.
Mine is built into the ignition switch. After you crank it turn the key back to the left slightly.
Can I do it myself, set the timing on my riding mower.
On most MTD riders it is right by the seat hinge on the right side as you sit on the mower.
Bypass the switch with a jumper & see if you can bump it with a hot wire.
Generally the ignition switch activates headlights on a riding mower and the start position only send current to the starter solenoid. If you turn the key and the engine cranks over than the lack of spark is going to be something else. If it is a riding mower you will have several safety switches to prevent start up under unsafe conditions.