Hello,
If the driver is an IVI driver, there is VERY likely a CVI version of it at ni.com/idnet (Click Search Drivers to find it). If you build a driver in the standard manner in CVI, you can automatically convert it to a LabVIEW driver (which basically preserves the fp tree, builds a dll, and uses call library nodes in LabVIEW to access the functions in the dll). You can certainly build a dll in LabVIEW and use it in CVI. I would try this on a simple set of the driver VIs, get it working, and then go through the process on the whole driver.
Repost if you have any other questions!
Thank you,
JLS