Buy yourself a Hayne's or Chilton's repair manual at any auto parts store. Here you will find the info you are looking for.
How do I get the starter out after I dropped it
The starter on a 94 Isuzu Trooper is located on the bottom, passenger side of the vehicle. It is found at the rear of the engine, at the flywheel.
From what I understand, you have to diconnect the exhaust system on the side that the starter motor is located on. To reassemble you have to replace the exhaust gasket with a new one. If you are replacing the starter, there is a GM starter that is a direct replacement for the Isuzu starter and costs quite a bit less.
bypass key on a trooper
It is located on the flywheel.
Take out the transmission and there it is. The flywheel holds the ring gear for the starter. If your ring gear has been obliterated by your starter you have an issue with how the starter engages the fly wheel to begin with. Proper clearances, alignment and securing of your starter will make your trooper whole agian.
The starter for the 1992 Isuzu Trooper was a little difficult to locate, honestly. One may find it on the driver's side of the motor, directly above the oil pan.
If you have a v-6 engine the starter is located on the left side bottom of the engine and it is a job to change out. You will have to remove the cross member, the left side engine mount and jack the engine up as high as you can to remove and replace the starter... GOOD LUCK...
Ask a Mechanic or person who works on cars
To remove the starter on a 1992 Isuzu Trooper, first disconnect the negative battery terminal to ensure safety. Then, locate the starter, which is typically found on the engine's lower side near the transmission. Remove the electrical connections and the mounting bolts securing the starter in place. Once the bolts are removed, you can carefully pull the starter out of its housing.
Between starter and block this increases clearance between teeth and flywheel or flex plate.
I found that the easiest way to get to the starter of an 1987 Trooper II is to take the front right wheel off. You should see it right there, and with relatively easy access.