After doing some more reading about bike sizing, I'm thinking now that the salesguy that sold me this bike didn't know what he was doing. What I'm getting from various sites when looking into how to choose a proper bike frame size is that its very individual and there's no formula, but my inseam is around 88-90cm and my current bikes seat length is 52cm. I found a formula someplace that said a good starting estimate was inseam x 0.65 which would put me at a 58cm frame. Does that sound reasonable?

Also, does anyone have opinions on a 2006 Trek 1500? It seems very close to what I had in mind and there's one for sale used with a 58cm frame size where I live for about 750$ CAD.