If the clutch coil is bad it would be ok to just change the clutch. Clutches can be hard to pull off. The coil should have resistance and not be open. It might be hard to check because there is a diode that dissipates voltage when it is switched off. If the clutch is worn out you will need to replace the compressor. If the compressor is seized up you will need to replace the compressor along with the dryer and other parts. This will require a lot of cleaning. How do you know if the charge is good? On most systems, if the pressure is below 20 psi the compressor will not turn on.
Good luck.