Repair a Head Gasket and Cracked Block on a 2000 W Reg 2.4 Mitsubishi Galant

Things to consider when replacing head gaskets.

Steps

Be sure that it is the head gasket that is causing the problem. You can buy what is called a "block tester" that will help you confirm that it is indeed a head gasket problem.
Remove the cylinder head. You will need a very detailed repair manual for this step.
Take the cylinder head to a machine shop and have it leak checked and checked for straightness.
Check the engine block very carefully for cracks.
Re-install the cylinder head using a new cylinder head gasket.
Test drive and re-fill coolant level several times.

Use the most detailed repair manual you can find.
Always take your stripped down head to a machine shop; they will be able to ensure your head is not warped and will resurface it to prevent future HG issues
Unless you are a seasoned technician you should take this job to a repair shop.
Be sure that it is a head gasket problem. There are other things that it could be as well.

Don't try to use cylinder head sealant as they cannot be completely flushed from the system.