Quesnel is serviced by Central Mountain Air, out of the main terminal at YVR:

http://www.flycma.com/

You'll likely fly on a Beech 19 Turboprop.

So if, for example, you take United out of Tampa and change planes in Chicago you'll be in Vancouver mid-day. You'll then be able to connect with an afternoon flight to Quesnel. You'll have to clear Canada customs in YVR and the check in again at CMA, so be sure to allow enough time.

If you're going to rent a car another option is to fly into William's Lake, which is a little under an hour's drive south of Quesnel. In addition to Central Mountain, you can also fly into William's lake on Pacific Coastal Air:

http://www.pacificcoastal.com

However, Pacific Coastal operates out the "South Terminal" at YVR which is the "old airport" so you'll have to take a shuttle bus to change terminals. There are details here:

http://www.pacificcoastal.com/flights/check-in.html

It's not difficult, but does add another layer of complexity.

Cheers,
Geoff Glave
Vancouver, Canada