Dear Gdvp
Do let me know whether any of your colleagues in your organization have designed ISO 14001 earlier or not? I am not asking about you, cause as you raised this thread it is very well understood that you have no prior experience on the subject. Once I know this I will guide you exactly...
If you have one person who is having expertise to design and implement the system internally then you can design the system yourself. Or else it will be very difficult to handle independently. Please take the help of a consulting organization.
We are helping many companies in getting management system certifications...Not only ISO 14001, we help in other management system certifications like ISO 9001, OHSAS 18001, Responsible Care, SA 8000, etc.
Do let me know if you looking for getting an external consultancy help.