Working in Fort McMurray is pretty much the same as working anywhere else in Alberta, except for more money and much higher housing costs.
If you have a camp job or LOA then the housing costs don't mean anything. CNRL on their Horizon project flies workers directly to the site in chartered 737s.
If you work residential, a buddy of mine is running a union (Local 424 IBEW) shop, paying industrial rate. They're crying for people. Of course there are all the usual running shoe outfits around too.
If you have industrial experience then it's no problem to get on with one of the non-union shops like Flint. The union shops are a little harder to get into because there have been a lot of layoffs recently with the construction phase of Syncrude UE-1 winding down. About 35% of the local's members are on the books right now. Even there though if you have a combo ticket (Electrician/Welder or Electrician/Instrument Tech) or specialized training like MI cable splicing you'll go to the head of the line.
As far as showing up in the morning and having a job by the afternoon, I don't think it would take that long. Residential construction is still going crazy, industrial is humming along, and two big condo/retail towers downtown (28 and 31 stories) will be breaking ground in the next month or two, with two more in the planning stages.
As for how long the boom lasts, that depends on the price of oil, pure and simple. I came here in July, 1998 when the town was about 35,000 people. It's now at about 62,000 and the projections are for 100,000 people within another 6 years if things keep growing as they are.
The U.S. government now officially recognizes the oilsands as being the replacement for oil from Saudi Arabia. Recoverable reserves using current technology are only slightly less than those of Saudi Arabia, and possible and probable reserves are 5x those of Saudi Arabia.
So I guess the bottom line is that like anything else in life you pay your money and you take your chances. Don't come here without a trade or a confirmed job because the streets are NOT paved with gold, just the same as anywhere else.