It's worth about $13,000. See quotes at http://www.edmunds.com/gmc/sierra2500hd/2006/index.html
The 2006 GMC Savana runs on regular unleaded.
The 2006 GMC Canyon runs on regular unleaded.
The 2006 GMC Yukon runs on regular unleaded.
The 2006 GMC Yukon-XL runs on flex-fuel (unleaded/E85).
The 2006 GMC Sierra-1500 runs on regular unleaded.
The 2006 GMC Savana-Cargo runs on regular unleaded.
The 2006 GMC Savana has a 4-speed automatic.
The 2006 GMC Yukon has a 4-speed automatic.
The 2006 GMC Canyon has a 5-speed manual.
The 2010 GMC Yukon runs on flex-fuel (FFV).
The 2015 GMC Yukon runs on flex-fuel (FFV).