Does an increase in hash/s decrease the time it takes to obtain a block or does it increase the possibilities of solving one? I am a total noob, and I've been reading the wiki for a long time and have yet to understand the basics... My question here is that if I were to mine at 100GH/s (example), is it guaranteed that I would find a block after a determined amount of time? Or does it just increase the possibility that I am the first to find it?
Since solving a block is a probabilistic math problem, having more hash power will increase the probability that you will find the right hash and solve the block. You cannot be 100% sure of the estimation given by the profitability calculators.