After replacing fuel filter, what should I try next?

I posted on the other site as well. i wanted to make sure you got the mail. Unless i did something wrong, I have 3 confirmed codes: 1336, 325 knock sensor? and 340 camshaft location sensor. Do I need to change the distributor? I will be gone for a couple hours taking mom to doctor. I wanted to be sure to have this done

I will tell you this, in the last 6 weeks or so i have had to replace 4 of these distributors...very common problem with this engine!!! No two will act up the same. That is all i got for you...

i am changing it