What you're describing is several different programs. CAD to design/model/draw your airplane, FEA for structural analysis, and an aerodynamics program to analyze its performance. CAD is approachable for the amateur, ranging from simple drafting programs to professional (and expensive) solid modeling systems. However, FEA is not something that an amateur will be able to get good results with (you need a thorough ground in structural analysis to set it up and interpret the results), and the available aero packages like AirplanePDQ, while useful for preliminary work, make many simplifying assumptions and thus are no substitute for a proper aerodynamic analysis.