on that latch--- remove it from the car & soak it( I used muratic acid)
I only soaked it for a short time/rinsed it off & then coated it with spray lube---this method cleaned up my latches so well -- I quit looking for replacements.
I only say this since your springs were so rusted it wouldn't open , the amount of build up inside plus the factory packed grease might be unusable (hard).
Lawrence