did this a few years back, i'll give you a few hints!
1. the bigger the heli the more stable it is
2. electric has less wobble than nitro
3. to get it spot on it will cost you about 6k-14k
I used an electric joker ....
http://www.joker-usa.com/maxi-joker2.htm
which is the largest electric heli you can get. it had full stabilisation so you take your hands off and it is stationary. Still have the heli,blades motor and esc if you are interrested in getting into it has no electrics bar those bits tho, i'll it in in plat classifieds if you want! or will swap for a nice marker!!!