Agreed on both counts.

20 MHz is well within the range of any random scope, and you should have at least one "any random scope" on your desk if you're doing electronics seriously enough to reach the "diagnosing QA fail boards" stage. So probe the damn thing - and see if the crystal ever reaches a stable operating frequency once the board is powered. That would tell a lot.

And yes, the "holy book of SMD passives" is a must too. They cost you what, $40 each? And can save you days of waiting for the "right" passives to arrive when you need to test a circuit change. You don't need to have every size - footprints are negotiable when you're hand-soldering - but you should have at least one Book of Many Resistors and one Book of Many Capacitors.