Went in for first oil change at 1000 miles. Told mechanic it took 5.5 quarts oil, but mechanic wasn't convinced it took that much. So he insisted on starting engine at 4.5 quarts for a minute or two then checked for proper level. Convinced, the last quart was added. Any chance there was any engine damage running the engine for such a short time 1 quart low?....Dumb question but will ease my mind. Thanks

You'll be OK, 4.5 quarts is plenty of oil to give you oil pressure and lubricate you engine.

Go by whatever the manual states. If it states 5.5 use 5.5, if it states 4.5 use 4.5. Simple as that.

You'll be fine but I suggest switching to synthetic at 3000.

Check whether the engine is in good condition or not.

There's no problem with starting the engine with only 4.5 quarts of oil in it on an oil change, there will be no damage from this. Most oil change places will have their technicians put in 4.5 quarts first and start the engine then check the level after shutting off the engine, topping off if necessary. Better than over filling an engine by someone not paying attention.

You should tell us about your engine. For 2.4L L4 engine like my 08 LT2, 4.5q should be enough. I would not go over 5quarts as the manual list that is the capacity of this engine. I have changed oil 5 times so I am pretty sure about it. Do not just idle the engine for couple of minutes. Drive around for 5-10 minutes. Then measure it you will see it gets to correct level. Your engine will not be killed in 10 minutes if it lacks a quart of oil. But driving car in long period with overfilll can cause big problem as stated in the manual. Here is the excerpt from the UM on overfilling

"Notice: Do not add too much oil. If the engine
has so much oil that the oil level gets above the
upper mark that shows the proper operating range,
the engine could be damaged."

The first time I changed my oil I got into the mistake like yours. I put in 5.5 quarts because I did not idle the engine warm enough. The UM says that the engine must be warm and you also need to wait several minutes for the oil to drain back to the oil pan to get accurate reading. The next day, after got home from work, I rechecked and found it was way above the top level. I decided to redo it and put in only 4.5 quarts. Since then, I always use only 4.5 quarts and my dipstick always shows full when the engine is warm and 3/4 full when it is cold.