Hi,
Unfortunately we don't do that kind of migration. Because migration process is very problematic. A proper hosting is required to run the migration, and it is most likely a problem will occur if you have too many products/orders.
We prefer not to do that. But you can check google.com and
forum.virtuemart.net
There are thousands of discussion about this migration (the fact that thousands of discussion actually proves how problematic the migration would be)
Normally, the migration is not a challenging thing, with a one-click, the process should run smoothly, but the fact that it usually won't.
About the CoolMart question. If you have little CSS knowledge, you can arrange things. If you want to use large LOGO (horizontally), then you shouldn't be using official CoolMart layout, because currently the "LOGO" and the "Main Menu" are staying next to each other. If the logo is too big, then there won't be enough space for the main menu.
If the dimensions of LOGO, as you see in the Live demo, is suitable for you, then no need to worry about it. Because your logo will be resized automatically to fit in that space and everything will be ready to go (unless you set a new dimensions for logo through template CSS file then it might corrupt the layout, because as i said, if the logo gets bigger, there won't be enough space to put the main menu next to it)
Regards,
Support