Moving site to a new system

Hi, Im looking to transfer my current website from its current system to oscommerece. The system i use now is a custom code based on oscommerece. i already bought a new oscommerece template and i would like the new admin system to be oscommerece. I would like to make some small designs and features changes to the templates to fit my needs and will need to use the same payments system im using now (paypal and credit card) , very basic things. it is very important to have all the admin options i have now... stock control, order print out etc... also, very basic oscommerece things. My current website is - [[login to view URL]][1] Thanks.