Dont start with an imac plane. From personal experience get a 3d capable sim such as afp, get a profile funfly or a foamy and practice practice practice.... The big trick to 3d is having a capable airframe and reliable powerful motor so make sure you have these before attempting anything.
The profiles are easier but if you crash no great money loss. There are some really good howto's and videos out there that you should read also, others can point you in right direction as I cant remember where they are. Have a look at http://www.flyingcirkus.com/ at the 3d university videos.

After you can torque roll and the rest easily then try 3d on an imac plane.