The 2008 V was a good year/vintage.
1) How much is the seller asking?
2) Get the VIN and go down to your local Cadillac dealer. Have them run a Service History on the vehicle so you know what your'e getting into.
3) No major service required.
4) Good luck getting an extended warranty that covers the top and its electronics. If out of warranty, the GMPP is not available. Save your money. The model years after 2005 have been the most reliable anyway.
5) Read all the online posts you can to get educated!