As to the yeast, it may depend on the pack you got. The age of the package affects the viability quite a bit, so check the date on the package for some indication of how fresh those cells were. Wyeast packs have that small amount of food in them that helps wake the yeast and get them into eating mode, so using that time is the best. Even better is making a starter. Though not required, and packs will make beer, I think it makes good sense to ensure that the pack to which one is about to entrust a day's labor and ingredients is healthy and able to make a great beer is worth the effort.
I think your results this time are hard to predict. The longer it takes for the yeast to get going, the more opportunity for something bad to get a foothold. Once the yeast does get going, there should be enough CO2 outgassing to keep out more nasties, but you'll want to package this beer soon after the fermentation is complete and it has been at a terminal gravity for a couple days. If your vessel is not airtight, you'll want to minimize the days it is sitting without positive out-flow from CO2.