Hi there, The best way to figure out if a boat is right for you is to go for a water test, ask the seller to give you some time practicing loading and unloading the boat if its and area of concern and spend some time driving it in the conditions you will be using it. 520 is a great starting size as it big enough to go just about anywhere while being a very manageable size for solo launch and retrieve. As far as boat show/vs dealer the offers vary but i wouldn't bother waiting months and missing the best time on the water, if theres one near you in a few weeks by all means go and see.
Haven't owned or spent much time looking at the formosa range but they get a very good rep, check boat sales for prices and compare to see if you're looking at the right deal. What motor, trailer and extras are with the boat?