The filler neck (t-stat housing) is held on by 2 bolts. Remove the bolts. As far as the inlet pipe, it is bolted in place. Remove the bolt and carfully turn it while removing it. There is an o-ring at the end. Make sure to replace it. If the tube breaks or buckles, you can get a replacement for it at most parts stores. They are about 15 dollars. As far as looking for the leak, get a pressure pump for the cooling system and pressurize the system to check for the leak. Also, make sure the hoses are in good condition before reinstalling them.