If you listen to your local fish store personnel, you have an extremely high probability of failure. Listen to experienced aquarists and have a great aquarium. It is entirely up to you.
That says it. I am VERY new to this hobby, but it is just like anything else I have ever gotten into. There are idiots and experts and all in between, you gotta learn to filter out the BullHockey. Unfortunately alot of the people at LFS's and retail stores that sell fish either don't know crap, or really don't care about the hobby, just money. So what you get is bad info, unnecessary money spent, and dead fish...which ultimately may lead to disinterest. This is very common, not just in this hobby.(Except for the dead fish part)
Your best defense from failure is patience, research, and advice from experienced aquarists. The last being the most valuable (IMO). If you get the impression from someone here that they think you are making a mistake, it's probably because they have already made that mistake. Learn from it. Later down the road, with a little more experience under your belt, you may "push the envelope" a little per se'. But for now, keep it safe.
Just about every post made here has good advice, but there are more than one way to skin a cat...for example...I am not patient. So I knew the "fishless" cycle was a last resort, but the last thing I wanted to do was kill fish. Period.
.............Enter Bio-Spira..According to Marineland this product will instantly cycle a tank by adding the nitrifying bacteria straight away. This will allow you to add fish immediately, but I would choose them wisely. The Cories you have are tough, but 2 or 3 will not produce enough waste in a 29g to keep the Bio-Spira alive. If you could use Bio-Spira, I would add maybe 6-8 Danios or some Black skirt Tetras or another hardy fish to support the bacteria. Without Bio-Spira those fish will have to endure the ammonia and nitrite spikes associated with cycling naturally. This may not kill them, but as others have said, not exactly "Good Karma".
I have a 29g, and I used Bio-Spira. I added 6 Danios and 4 Black skirt Tetras with the Bio-Spira. 5 days later 2 Honey Gouramis, 1 week later 3 gold barbs and 1 Opaline Gourami. For the first 2 weeks I checked water parameters DAILY, and did 25% changes every other day or so. The Ammonia and Nitrites spiked at less than .25 ppm, and within a week after startup I was testing positive for Nitrates. Now, a little over a month after startup I test every other day, Ammonia = 0 Nitrites = 0
So in conclusion. Take your time, ask lots of questions, pay attention to the answers, choose your fish wisely, use Bio-Spira if you can, TEST YOUR WATER!!!!!!