An easy option if it starts nuisance alarming at night, would be to just pull the connectors off the horns, you should still have the indicators flash.
Can't help with machanic's in your area, but any of the mobiles will come to you. Before you buy to many bits, especially head gaskets the head will need to come off first. It all depends on whether the liners are proud of the block, level or they have sunk.
One other check while your checking everything Cobber suggested is the hose that goes to the ecu, if you have an air leak that could give the ecu the wrong info on engine temp.