Chevrolet Repair: 1996 CHEVY SUBURBAN TEMP GAUGE, chevy suburban, temp gauge

Question
I have a 1996 chevy suburban 1/2 ton 6 cylinder, that is reaading high temps on the gauge.  Went to auto store was told to replace temperature switch, lost alot of coolant when that occured but assumed that it would replenish with the reserved coolant?  When we started the Sub again , the gauge went past 260 and has been reading that ever since.  Could have there been an air pocket formed while replacing the switch or should we also replace the thermostat?  Would this problem also be cause the engine to short out every time I start it causing it to hesitate upon putting it in drive?

Answer
Hi Eve... When you replaced the temp sending unit you should have refilled the system with coolant, then you need to bleed it... if you are have an over heating problem changing the thermostat would be a good idea... you will need to bleed system then as well.I don't believe that this would be part of the stumble that engine has when shifting from park....hope this helps