Proper Radiator flushing / Refill procedure for 95 SS impala

Went to our local auto part store in search of a repair manual. In looking at the radiator in my 95 SS it has no drain that is visible and it has no radiator cap… I’ve always added coolant via the reservoir tank.. The car was originally my mom’s car and has not been driven in some time, it has the original coolant in it and I suspect that the heater core my be somewhat blocked as the heater does not function too well..

P.S. I am replacing the radiator too, it has cracked and is leaking. I have the new radiator and have not installed it yet. I thought it would be a good time to do the hoses, thermostat and fluid change. Not sure does the 95 use Dexcool or the older green fluid?

Thanks in advance for your assistance.