PLease help, overwrite from one page plugin from linelab.org

[xaemax]

hi a few months ago i purchase a subscriptions with linelab.org and everything was fine, but right now i have a problem with their one page plugin. i really need solve this.i buy a component named preorder for virtuemart, than i need turn of the one page checkout plugin because if i dont turn off i'll not able to have the preorder option active. however i try unpublish the plugin, unistall erase the old files of the plugins and nothing happens, right now i cant see the terms and services link, i try reinstall virtuemart, anything work. the coupon button is not working, i need to solve this and i cant find the correct file trace of the cart to override because when i try to uninstall the virtuemart to install again just give me an error 500 in my whole site go down. please can you say me where is the files of the cart or what happens? THANKS I REALLY NEED SOLVE THIS! my site is inwebmanager.com and the cart page is here: inwebmanager.com/apps/cart i'll waiting for your answer, thanks in advance!