Donna, if you refer to the schematic you mention on Tom's, from the start page in the PDF, do a search (Ctrl-F) for X3, which should take you straight to the page showing your board's system timer. Even if the schematic doesn't make much sense to you, you should be able to identify the parts shown there: X3, U54, C461 and C462 on your board.
If the chip that does not seem to be present is actually the larger chip completely circled in your image, it's the X3 written underneath the red ellipse that is for that chip. The C461 & C462 are the tiny capacitor chips between it and the clock synthesizer chip U54. The chip you have circled has the crystal frequency silk screened on it, and from the schematic its variant is X-14D31818M-37GP.
If you wanted to get the exact thing for a technician to try, I'd suggest try sourcing a same model board that is condemned for a different fault (therefore maybe free?), and a tech with SMT soldering gear should be able to transfer it.
If you simply want to try with a new component, I can't say how difficult it might be to get the exact part, but something that seems to be an equivalent will possibly function fine, but that's an assumption.
Edit: I'd re-iterate my comment above, before trying to "repair" anything by part replacement, make sure the board doesn't simply have feedthroughs to the other side to accomodate a crystal in a package that won't fit on that side.
Edited by Platypus, 05 June 2016 - 08:48 PM.