Need new bolts for intake manifold?

Start by disconnecting the battery and draining the coolant. You don't need to replace the intake manifold bolts, you do need to remove the valve covers. I would get the updated metal-carrier (aluminum-reinforced) lower intake manifold gasket set.

Example: Fel-Pro “Problem Solver” set (often listed as MS98003T) or equivalent.

When you are done with the job change he engine oil and filter and refill the cooling system. Allow the engine to warm up with the radiator cap off, as the engine runs and heats up watch the coolant level and fill as needed. Reinstall the cap once the system is full and the cooling fans have come on. Let us know if you need anything else.