Not just a good locksmith but a very good one..
Some dealers can provide SOME keys,, Ignition key may be common GM key (or not) which you can get most anywhere.
But Tri-mark keys (common for doors and compartments) their key blanks are kind of rare,, I have found one store that stocks them (Gilroy's DO IT hardware, Davison, MI) and a couple of locksmiths that have some of them.
You can also order the blanks (expensive) or even the cut keys from Tri-mark if that is the grand you have.. some do, Some do not.