Yes you can disable the siren without any problems. The siren has it's own set of small rechargeable batteries. When they start to go bad the siren will do wired things and go off on it's own for no reason. It is a bit of a job to get the wipers off, but the cowl removal is simple after that. You can use the search box at the top of the forum page for siren and all kinds of info will show up.
You may want to check for any Diagnostic Trouble Codes, DTC just to be sure something else isn't messing with you.