Paypal pro and 1.3.7.1

I am using version 1.3.7.1 and I want to add paypal pro so I can take credit card payments on my site.

There is no option to do this when I go into admin / modules/ payments.

I have asked my website co. and they say that I cannot simply bolt paypal pro onto my zencart version 1.3.7.1 and that I will need to upgrade my whole site to 1.3.7.8 which will cost several hundred pounds.

I don't really want to do this as 1.3.7.1 is working fine for me.

Can anyone tell me is this correct and can I really not add the paypal pro to what I already have. Just want to check before I go ahead and spend the money to upgrade
Thanks

PayPal Website Payments Pro (WPP) is only available as a default payment module in Zen Cart version 1.3.8a.

Before performing any upgrades, it would be good if you first check with PayPal whether you are eligible to sign up for that program (WPP) as a merchant first.

For the Zen Cart upgrade from 1.3.7.1 to 1.3.8a, you can either do it yourself or let your host do it for you.