My computer may be bad

Just purchased my car 1 previous owner with only 140 k original miles it is a 1994 Buick LeSabre limited

I have a security warning light and if hooked up horns go off constantly

Also have the service engine soon light and scanners will not connect with the computer

Buick does not even keep the tool on hand any longer which is OBD1 NOT OBD2 which came out in 1996

Asking opinions on if this is a computer or a wiring problem and where is security system installed at so I can work on it

I may have contact soon with Buick Mechanic of 43 years working at the Dealership

And will post any fixits I get along the way

Thanks for any and all response's