Are you just getting the lower and upper intake manifold gaskets replaced?
Are you going to get a new upper intake manifold, or at least get the reduced diameter EGR Stove Pipe that goes into the Lower Intake Manifold?
I would say you could try to tell them you will provide the parts, but most shops won't go for that because they need to mark up the parts so they can cover their labor warranty charges.
Here are the parts I'd get for it, unless you have, or ever plan to add mods that increase HP, then you'd be better off with the AC Delco 2nd design LIM Gasket.
Upper Gasket Kit
with Reduced Diameter EGR Stove Pipe, Thermostat, Thermostat Gasket (rubber one), Coolant Water Bypass Gasket, Throttle Body Gasket, Fuel Injector o rings, coolant elbow o rings ( the coolant elbows I'd replace totally, and use the GM coolant elbow it is only around 7.00) and you also get an EGR Gasket.
DORMAN Part # 615207 33.79 at RockAuto
Lower Gasket Kit
FEL-PRO Part # MS98014T 51.79 at RockAuto
So 86.00 for UIM & LIM Gaskets, and figure some money for coolant to put back in it.
I'd figure a shop charging at least 150.00 for those parts, as well as charges for 3-4 hours of labor (120.00 - 240.00 depending where you go) so I'd expect to pay from like 300.00 - 400.00, realistically I think 600.00 would be what most are going to charge you if they replace both the upper and lower intake manifold gaskets.
If you want to see how quick a pro does the job check this out.