Not sure what type of AC system you have but on my 2002 with an Evans system the expansion valve is located under front hood and attached to the evaporator coil. Easily accessed from hood.
Expansion valve wrapped in insulating tape
Replacement of the expansion valve would require recovery of freon in system.
R&R of expansion valve and receiver dryer.
Vacuum system down
I have friend that can do the recovery and recharge, so I may have him do the recovery I will replace components and flush/inspect then have him recharge. Or may have him just do it all.
Edit: not sure why images are not showing up!