I won't recommend you to waste your time on it.
It will require advanced PHP and CSS knowledges. Otherwise there will be lots of conflicts. (CSS and JavaScript conflicts)
Migrating 2 templates (2 virturmart templates or 2 joomla templates, doesn't matter) is no difference than building a template from scratch. Without knowledges of PHP, CSS and little bit JS; you can't avoid conflicts and layout issues.
Regards,
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