have to upgrade just to use paypal Payment pro?

I recently installed 1.3.7 and now relize i'll have to upgrade in order to be able to use the Paypal Payments Pro (to accept credit cards on site and not be directed away). Is there any easy way to upgrade the site without losing all the customization .. just to get the payment mod? I've never been good at upgrading and is why i try to avoid it at all costs but this time I don't think I'm going to be able to. any suggestions would be great .. the main customizing i did was just to wordings, images and templates. the site is https://www.arcana22.com and the version specs are
Zen Cart 1.3.7.1
Database Patch Level: 1.3.7.1
v1.3.7.1 [2008-08-19 18:44:55] (Fresh Installation)

Server Host: https://www.arcana22.com (216.180.255.105) Database Host: localhost (127.0.0.1)
Server OS: Linux server78.mcbride-designs.org 2.6.18-53.1.14.el5 #1 SMP Wed Mar 5 11:36:49 EST 2008 i686 Database: MySQL 5.0.51a-community
Server Date: 08/29/2008 11:13:49 Database Date: 08/29/2008 11:13:49

Server Up Time:
PHP Version: 5.2.5 (Zend: 2.2.0)
HTTP Server: TimmiT HTTPD Server powered by Apache

If you've done the customization correctly (used the template/override system), then you won't lose your changes when you upgrade, but it will help if you have something like WinMerge or Beyond Compare to compare the contents of your modified files to the 1.3.8a versions.

To enable Website Payments Pro, you need 1.3.8a or newer.
There is no "patch" to add it to older versions for various technical reasons.