If I understand right, you want to remove VM Invoice from your Joomla installation.
I have no script to do that, but you can do it manually by removing all files and folders + removing data from database.
Look into administrator/components/com_vminvoice and there should be file vminvoice.xml. It contains info about all files and folders you have to remove. Site (components/com_vminvoice) and admin part (administrator/components/com_vminvoice) + language files (languages/{lang}/{vminvoice-files} AND administrator/languages/{lang}/{vminvoice-files} ). Do not forget on plugin in plugins folder.
In database remove all rows from components what have option=com_vminvoice in admin_menu_link. Also table plugins have info about plugin. If you want to remove vminvoice tables, there are probably 4 of them.
I think, that should be all.