It sounds like you haven't fully researched your options. The quote mentioned 5 oz. Dacron and 1 reef. The last post mentioned offshore sailing and heavy duty reinforcement. These two options are at odds.
First, your Tanzer 7.5 is not what I'd consider an offshore boat nor does it appear that you are likely to be in heavy weather for extended periods, living in Quebec. I'd check with a couple of reputable sail lofts and get their opinion on the kind of sail (cloth weight, number of reefs, etc.) suitable for the type of sailing you intend to do. You probably don't need a bullet-proof, heavy sail with 3 reefs if you are going to choose to sail only in light or moderate winds. Adequate reefing (I'd go for at least 2 reefs) should get you through brief, unexpected periods of high winds.
It's a good idea to verify the measurements for your boat. Hopefully you didn't take the numbers from an old, stretched out sail. I just went through a sail measurement on my own boat yesterday. Even though we had the architect's drawings and the 10 yr old sail it's replacing, the sail loft (which is nearby) measured the boat. A reputable sail loft would tell you how to do this yourself. Assuming your boat is on the hard for the winter and the spars are accessible, it should be relatively easy to measure for a new main.