Hi,
HikaMarket 1.2.0 requires HikaShop 2.2.0.
The "HikaShopPaymentPlugin" interface is a new feature included in the latest version of HikaShop. That's why it can't work in your website, you have an older version.
By removing HikaMarket, you won't remove the Paypal Adaptive Payment plugin.
But you can unpublish it.
If you have the problem with the payment plugin, you may have other problems in HikaMarket. It requires HikaShop 2.2.0 but not only for the payment plugin, for the multi-shipping too.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.