hi ,
first of all
to add shop to the client you need to add it throw gameserver.opt file
you'll find line : S:game.url_list
in this line you'll find line like this
|shop.url|

simpley replace

.. by you're shop link
if you want shop i'll suggest to you this release by revolution team

follow the steps ..
for the autopayments i think you need to open a business paypal account and you'll find documentation on how to do it ...
for the npc sale quick things are you talking about drops ?
if that the case then you can create LUA Script that sell auto this drops
else i suggest you that you install server ver 9.5.2 i think it's the best version so far if not 9.1 better for sure then 9.4
good luck