Hi,
I am a Joomla developer and working with Joomla since its version1.
As your website is Joomla2.5, I guess your VM version is 2.0. So, along with Joomla, Virtuemart also need to upgraded to Virtuemart3.
I am a core Joomla developer and have upgraded/migrated many Joomla websites with Virtuemart.
I can do it, I am here, just give me a knock.
Regards
Mohsin