Hey junglejim
nice find from ebay huh, i have found a couple of systems on there with great prices!
anyway, no, your pioneer burner is NOT DL capable.
however, internal drives (i love pioneer drives by the way, been using them for close to 7 years now strictly for DVD authoring) are really inexpensive and very easy to install.
the one installed on my mac is the Pioneer DVR-111D.
it took me about 4 minutes to install and about 2 minutes to download patchburn from the internet, install it, test compatibility and in less that 10 minutes i was burning discs from within DVDSP and iTunes.
one thing to keep in mind: if you purchase an internal drive and install it yourself, you will need to download patchburn for any Apple software that burns directly from the application to be noticed, AKA "SuperDrive"