I had about 70 RC helicopter flights under my belt, and about 8 hours of RC plane simulator experience when I started learning to fly planes. I soloed in 3 flights. I also crashed my trainer 6 solo flights later [:'(] !

The sim will save you many hours/flights at the field. As da Rock pointed out, you can turn on wind and gusts to give yourself more of a real world challenge.

You'll still need an instructor, and there are many things to learn that the sim won't teach you (plane assembly & setup, radio setup, engine tuning, etc.), but a sim is well worth the cost IMO.