No questions are dumb if they lead to a greater understanding and enjoyment of your bike.

Yup, an aluminum (aluminium?) bike will be light, but will also be stiff. Skinny, hard tires don't help. Wider tires are the easiest way to increase the comfort of a bike. (Secret, they'll even be faster. Studies prove 700x28 is faster on normal pavement than 700x23, because you get a smoother ride, wasting less energy)

To find the size your bike will fit, as canam73 said, measure the clearance around the tire. I'm afraid that your bike will most likely have quite limited clearance. It has been designed around short-reach brakes (39-49mm), so you'll be able to fit 700x25mm tires, and maybe 28mm. Definitely no bigger. Fit the biggest you can. Unfortunately, some makers label their tires inaccurately; their actual size will be bigger or (usually) smaller than the label's size. For my bike with the same clearance limitations, I find the Grand Bois Cerf Blue tires at 27mm are the most comfortable it can fit.

There are some bikes that aren't so racy and fit wider tires. "Classics" bikes (like the Specialized Roubaix or Trek Domane) are just a little bit less agressive, for more rough-surface riding (supposedly inspired by the classics races on cobbles). Cyclocross bikes are still quite fast but have room for ~35mm tires.

You could also change to a smaller wheel size (650b) to get more brake clearance. But the necessary parts (new wheels, tires, brakes) would cost you about as much as you spent already.

Fit the biggest tires you can and enjoy the ride. Then, upgrade once you know what you really want in a bike.