If the clutch will not release, there are a number of ways this can happen, but you are not stuck as long as you have a good battery.
Put the vehicle in second or so if you are on a level or down grade and not heavily loaded of course if you are.
You probably know about what sound your car makes when you shift it as you are driving it will start at a low frequency and get to a higher on then you will push the clutch and let off of the gas and shift the lever to the next gear.
Without the clutch you must just match the sounds from high as you push the lever out to low as yo let off the gas and push it into the next gear.
I promise if you have never driven a big truck it will seem strange and be a little hard to do, you must push the lever out just as you let off the gas so hold a little pressure against it as you let off and you can feel it loosen then just push it quickly out and toward the next gear, do not take your foot completely off of the throttle jus let it go back to low.
It may grind a little, do not force it it will move in a little,, then you push it on in and ease into the throttle, if it does not go all the way in just give it a little and let off and most times it will go on in.
It is a trial and error thing you will have to learn,
Good luck, it is a good idea to learn this type of shifting you may need it at an important moment.
If the clutch is slipping and will not engage, a hydraulic clutch out of adjustment can build up fluid in the slave cylinder and not return to engage. If you can get the line loose on the clutch "master cylinder" and bleed it, you can do the clutch-less shift if it reengages.
A diaphragm type clutch can over-center and stick to the floor it is dangerous and hard to flip it if it has so unless you have good open access to the pressure plate and a way to jerk your hand and tool out of the way I would not fool with it.
Just chatting away. Some like to run, in church, during prayer. Little rascals can get quite a ways before parent catches up to them.
