RobertA

firstly all firms in perfect competition are price TAKERS ie don't set the price themselves. They choose to produce at the level where price = marginal cost. ie the cost of producing one more unit is the same as the revenue they get from it.
Whether or not they make profits depends on whether the price is above or below their average costs.
You are right, in the long run they will make normal profits ie price will equal marginal cost.
Hope that helps