1996 deville do I need to bleed the cooling system?

if the radiator coolant translucent bottle reads "FULL HOT" and the engine is hot...and still you have no heat...I'd start lookin' towards the highest point comin' out of the heater core...sometimes there's a valve there just for that purpose...like a bicycle valve~ if not just pull the top hose off with the heater engaged and "belch" the system yourself~

there is a cable leading to a valve that switches the coolant flow on...the diverter valve...might be an electrical goodie, might be cable...you'd know when you engaged it~...but this valve may not be engaging either~ we'd have to test the components involved....also there may be a "blend-door" where the inside air is brought in and channeled to the defrost, face or legs~ this one too may have a cable...would have to study the intimate details of YOUR systems to peg a part that we could replace~ you could check the fuses...this would not cost a thing~

the car overheated, I replaced the thermostat and refilled the the coolant.The message on the keeps telling me to check coolant level. it is full in the tank. I am thinking there must be air trapped in the engine. and I don't know how to get out.

run without the thermo to be sure there is good circulation....panic fill with hose water? this can be deadly with aluminum heads that like to react with anything and everything...we even recommend that you use "De-ionized water" which is NOT tasty....and glycol 50/50 mix~ once flow thru the heatercore is established treat yourself to a brand new 195 degree thermostat~....we'll take it from there...remember....drain OUT the ol3' panic hose water and replace with proper coolant mix~'stokay?~

...again the heater control may be damaged or inoperative~ this will let us know~