There are a few good sims out there, which one is the best i dunno since i don't have one, Clearview and RealFlight just to name a few, If you have a local hobby shop they will more then likely have at least one of the good sims.

co-axial heli

Alrite a co-axial heli is more geared toward the begginer and has a upper and a lower rotor which makes the co-axials very stable
The two best co-axial heli's that come to mind are the Eflite Blade CX2 or the Esky Lama V4

[link=http://www.helidirect.com/product_info.php?cPath=29_223&products_id=4672]Esky Lama V4[/link]
[link=http://www.helidirect.com/product_info.php?cPath=29_224&products_id=2361]Eflite Blade CX2[/link]

These helis are designed for indoor use, You can fly them outside but the least bit of wind would prolly be disasterous, atleast from my experince with em.