Question about 2.4G remote

Hi Every C Hing, I am a "New Hand", and I have a stupid question is
I want to buy a 2.4G Remote ( Whether 3PK or 3PM etc...)
I want to use this remote in my Lazer ZX5
And the questions is:
1. Is that I want to change my original AM receiver to 2.4G receiver?
2. I have bought a "Analoge" servo recently, if I use 2.4G remote, can I still use it?
3. Beside those things mentioned above, does any parts I need to change to adopt the 2.4G Remote( For Example, I use the original Lazer ZX5 ECS, can I still use that, or replace a new one to adopt 2.4G remote?)
4. What is the main benefit of 2.4G Remote?
5. Which 2.4G Remote is better and please advise me the budget(full set, include receiver, remote etc....)

THX Every C Hing

1.yes, u need a 2.4G receiver
2. you can use whatever digital or analog
3.  just plug your new 2.4G receiver/remote, it will work fine
4.  just check it out: http://2.4gigahertz.com/features/features.html
5. 3pks 2.4g full set about $22xx, 3PM 2.4g full set about $12xx-14xx ? ( the update price, pls check at KWS) both two models are good for you, BTW, futaba will release 4pk soon.

THX Kaho Hing
I know more now la
I still have one more question is when I am using AM receiver, it need a crystal to classify the frequency, in 2.4G mode, it still use the crystal or not?

not, it will auto detect/ and auto change frequency