1) you can have a look, but it wont be as straight forward as replacing the values.
2) moodle upcoming versions will have additional payment gateways included in the core code, but not that you input credentials to choose your own, there isn't a few but many payment gateways across the globe, just take example of your region, there is JazzCash, then you'll like EasyPaisa, SadaPay and so on.
3) feasible yes, but easy: No, you have to have good knowledge of PHP to develop payment plug-in. alternatively you can post a job on moodle forum as well look out for payment gateway developers on fiverr who specifically develop plug-ins integrating jazzcash or similar into moodle.
2) moodle upcoming versions will have additional payment gateways included in the core code, but not that you input credentials to choose your own, there isn't a few but many payment gateways across the globe, just take example of your region, there is JazzCash, then you'll like EasyPaisa, SadaPay and so on.
3) feasible yes, but easy: No, you have to have good knowledge of PHP to develop payment plug-in. alternatively you can post a job on moodle forum as well look out for payment gateway developers on fiverr who specifically develop plug-ins integrating jazzcash or similar into moodle.