1990 trooper coolant leak INSIDE car

got to be from the heater---coolant leaking out of the heater addembly into the front passenger seat floor area

i assume i need to take this apart and look for a leak BUT any tips on where to look and proper steps to take---never done this before

thnak you

Most likely the heater condenser is bad.
Nowadays it usually means major disassembly of the dash to get to it.
If you don't have a service manual get one or find one online, it will be a big help.

You may be able to find an appropriate diagram here http://www.myisuzuparts.com/