You can refer to the Instrument Driver Network, www.ni.com/idnet for information on how to develop an instrument driver in LabVIEW. There is a section titled "Development Tools" that should help get you started.
With instrument drivers it is definately possible. The difficulty can depend on the instrument you are trying to develop the driver for, and also on how complete you need the driver to be, what percentage of the instruments functionality do you want to support in the driver.
On the website I mentioned there are guidelines on how to put an instrument driver together. There are also a number of other, how to use Instrument Drivers on NI Developer Zone that you may find useful. You can go to ni.com/zone and search on Instrument Drivers.
You may also want t o look into developing an IVI driver, in LabWindows/CVI (those can be converted to LabVIEW drivers). IVI is driver development standard that was introduced a couple of years ago to address many of the things that older standards did not, you can get an idea on how IVI drivers can be used in LabVIEW by visiting ni.com/zone and searching on "Using IVI Drivers in LabVIEW".