B737 FLT CREW FAILS TO REALIZE PDC HAS CHANGED THEIR DEP FROM LAS 3 TO STAAV 4.

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FOURTH AND FINAL FLT ON FIRST DAY OF PAIRING. I WAS THE CAPT AND PM ON FLT FROM LAS. DURING PREFLT; BOTH OF US FAILED TO SEE THAT THE PDC CLRNC DIFFERED FROM THE FILED DEP. DISPATCH HAD US FILED ON THE LAS 3 DEP; WHICH WE NEVER USE. PDC CLRNC AMENDED US TO THE STAAV 4 DEP. THE TWO ERRORS THAT OCCURRED WERE THE FO'S LACK OF EXPERIENCE WITH AMENDED PDCS AND MY FAILURE TO LOOK AT THE PDC CLRNC TO CATCH THE ERROR. I SHOULD HAVE CHKED MORE THOROUGHLY KNOWING THAT LAS NEVER GIVES US THE LAS 3. THERE WAS NO THREAT; JUST A LACK OF ATTENTION. I WILL BE MORE DILIGENT TO PDC AND RTE VERIFICATION IN THE FUTURE.SUPPLEMENTAL INFO FROM ACN 786096: EXPECTING AN RNAV OUT OF LAS. I SAW LAS 3 ON RELEASE. DISPATCH RELEASE SAID 'NON STANDARD RTE.' NEVER HAVING FLOWN IT; I DUG IT OUT OF MANUAL. WE BOTH FAILED TO UNDERSTAND THE WAY THE PDC READ; EVEN AFTER DISCUSSING IT. WE ENTERED LAS 3 INTO FMC. WE FLEW LAS 3. WHEN QUESTIONED BY LAS DEP IF WE WERE ON THE STAAV; WE SAID NO; LAS 3. DEP ASKED US A FEW QUESTIONS; AND THEN TOLD US TO CONTINUE ON LAS 3. A BETTER UNDERSTANDING OF PDC AMENDMENTS AND PUNCTUATION WOULD HAVE BEEN HELPFUL IN THIS SITUATION. ONCE WE DISCUSSED THE ABNORMALITY OF FLYING THE LAS 3; THAT SHOULD HAVE BEEN A HINT TO VERIFY WITH ATC AS TO WHICH DEP WE WERE EXPECTED TO FLY.