As others have stated, qualification level depends on gear, certain Canon equipment gets you points, you need enough points to qualify at a given level. Since you mention 'paying the hundred bucks' I assume you're thinking Gold level, that means 20 points. You mention a 60D and 24-105L, and I hope you have more than that - your 60D gets you no points, your 24-105L is worth 8 points, not even the 10 points you need for Silver level.
But an even more important issue is this:
I have a 24-105L that got a small bit of sand in the focus ring while shooting on a windy day at the beach
Assuming you have the points to qualify, you can pay your hundred bucks…but for the issue you describe with your lens, you'd be taking advantage of the 20% repair discount (and maybe the 3-day turnaround), but not
the free clean & check…that doesn't cover anything that requires them to do any disassembly.
11-point EF Lens Maintenance Service:
• Clean External Lens Optics
• Clean External Lens Body
• Check Lens Attachment and Removal
• Check Camera/Lens Communication
• Check External Lens Barrel
• Check Operation of Focus, Iris and Zoom Rings
• Check Operation of Tripod Collar (if applicable)
• Check Aperture Function
• Perform Simple Image Test (exposure, color balance, resolution)
• Tighten External Screws
• Verify Firmware Version and Update (if required)
I was at the Canon Service Center in Jamesburg, NJ earlier this year (I was in the area for business, and took my 1D X in person for the AF service recall). While I was waiting (they did it for me in less than an hour), someone asked about CPS cleaning and the rep told him it was good for bodies (they clean the sensor, mirror, and focus screen), but basically worthless for lenses, that you were better off waiting until your lenses needed service, since they do all that clean/check stuff as part of that anyway, and you can certainly clean the front and rear elements and wipe off the barrel yourself.
I'm not sure how much they'll charge you for cleaning the sand out of the focus ring, but I am pretty sure it will be much less than $500, meaning spending $100 for a 20% repair discount isn't really going to be cost effective unless you have more gear that needs repair or plan to send multiple bodies in for cleaning (or send your 60D in several times).