At last, I’ve succeeded in setting up a Debian router with CUPS and Samba.
As it turns out, the reason why Samba wasn’t talking to CUPS was because the spool directory did not exist. I’m sure I would have figured this out much sooner had I turned up the logging level while configuring. Eh, it didn’t take too long to figure out. Otherwise, everything has turned out fine after a proper upgrade to testing, except printing via CUPS to the multi-function network printer (a non-issue) and the fact that CUPS’ web interface is completely non-functional when it comes to adding new printers.
Incidentally, today is the more-or-less official start of Missy and I’s renting agreement with our new landlord. Now that this Debian box is up and running, I no longer have to worry about leaving my parents with a non-functioning network once I take away the wireless router, and focus on more pressing matters, like organizing last-minute FroshWeek details, and figuring out how to get all of my crap over to my new place of residence.