Again, 2 HP is all you need. If you put a 5 HP on it, she's just over powered and you're not really going any faster, just beating the water to a froth. The shape of Weekender limits her speed to about 6 MPH, so a bigger motor is just tossing more fuel into the tank, little else. The Weekender is a novice sailors boat. Why you managed to capsize her, I don't know, but you have to screw up pretty bad to do this. Typically, it's because you went out in way too much wind strength, for your skill level. On your first few sails, 5 to 8 knots, no more. It's damn hard to screw up bad enough to have anything more than a puff increase your heel angle in these wind strengths. Think of it as taking a race car out for the first time. If you start thinking about 200 MPH, you'll quickly find yourself in a world of hurt, but if you lazy around the track at 70 MPH, the worst that'll happen is you can bend a fender, as you get a feel for the car. As you gain confidence (this is what sailing is about BTW) you can considering pushing over 100 MPH or more appropriately, bigger wind strengths. Next time, take someone with you, so some positives can occur and your confidence can build. Light winds, until you have a clue about what to do, how to steer, which strings to pull, etc. In fact, learning to sail in very light wind strengths will make you a much better sailor, eventually.
Instead of lessons, just stop down at the local sailing club and volunteer to be "crew" on someone's boat. They're always looking for victims, I mean additional crew. You'll learn very quickly how the boat is handled. Let them know you're a novice and a bit scared and hopefully you'll not get a Capt. Bligh for your first skipper. They'll show you what's up, how to steer, set and trim sails, etc., all for free too. Ask questions, just to remind them you're a novice and with some luck, you find an old fart that likes the idea of getting yet another hooked on the sport, maybe in his image.