Oscommerce and Paypal Soloutions

i am new to this payment gateways and internet merchant accounts. I have install Oscommerce on my website . My client says that he want to have website payment pro as a payment soloution but would like to move on to payflow gateway. I have read that payflow gateway doesnot support the oscommerce . I am woried that if right now i have configured run the oscommerce with website payments pro and how would i manage later as i cant chnage shopping carts every day.. what can be the soloution ?

thanks in advance
Regards

You should agree wtih the client about each stage. Tell him you can implement the first stage for $ price. And if he want to move to something else it will take $ (and you can hire programmer if you cant do it by yourself)