1) check your door lock cylinder.
2) change your tranny fluid. For vr6, i would recomend Redline in the 75w80. weight. Redline transmission fluid also claims to stop rough shifting and grinding.
3) you need a new latch. any latch will work as long as the car it came out of looks like your chasis style.
4)which one? timing? that engine has a timing chain which requires an engine overhaul to replace.
5)Sounds like the speed sensor may need replacing too.