Bow,
I recommend you buy "Lock On Gold." This is a special edition that contains the LockOn game with the 1.2 update plus a second CD containing the Flaming Cliffs addon. After installing that, all you would need to get completely updated to the latest version is get the FC 1.12a patch from lockon.ru.
I got my copy of Lock On Gold from Overstock.com for $29.95
Hope that helps ya. Next time, you should be a little more careful where you post your question. This is an odd place to find a question like yours. You would get more response if you had posted in the general forum or even the "Payment Issues" forum.
How realistic is it? I personally think Lock On is state of the art for flight sims together with IL-2 Forgotten Battles and IL-2 Pacific Battles (if you like WW2 planes). The only competiton (IMHO) is Falcon 4.0 Allied Force. Many would argue (rightly so I think) that Falcon is more realistic than Lock On, but to me, LO wins in the "fun" category and it still excels in the "realism" category as well. I got bogged down with Falcon and just never got into it. This game was great fun from the minute I clicked the icon.