I can't recommend spinning highly enough for anyone!! People of all sizes spin at my classes. I've been to several! It can be as hard as you want it to be or as light as you need it to be. The instructor is just there to guide you. They want you at YOUR max, whatever that might be.
You will hurt the first few weeks.
Especially the rear end. Also it works major muscle groups in the legs that may talk to you for a while. When I first started my upper body also ached tremendously, so it must do something with the upper body. I think it must work the core because it was hard to sit upright those first few weeks.
It is THE best workout! I started at 235 pounds, no problem. My best friend started at 265 pounds, also no problem. We're both avid spinners and we've both lost 80 pounds.