My key will no longer open the trunk on my 97 GT. I have a trunk release button in the glove box so I can still get it opened, but what would be a fix for this? Any ideas?

 

What do you mean it won't open it anymore? has the key cy,inder fallen out? or does it now turn in the cylinder?
You can either buy one cylinder just to replace that one, or buy a whole set to replace tham all. Some dealers can set they new cylinders to use your old Key also. You can also go to a lock smith and see if they can replace it and match the cylinder to the old key.

 

There may be no need to replace the lock cylinder. First take a can of spray silicone lubricant and spray the key on the metal, cut portion (ideally use an original key not a copy). Then put the key in the lock and take it out. Do this several times and then try to turn the lock and keep lubing the lock. The locks on my 96GT stopped working and I just lubed them and they all work flawlessly now.