How to change anti-freeze, any thing I need to know that is important to this car other than the basics ? I can do most simple repairs

system anti-freeze = type that fits your vehicle and the correct mixture

All Cars and Trucks need anti-freeze (for cold)/coolant(for hot) (same thing). If your car runs as is it has it, but if it's not been changed/serviced in the last 2-3 years it may be due for an anti-freeze/coolant replacement service.

This is covered in the Owner's Manual. Please Read It.

GL,
TD

The square yellow lid is the filler for the radiator. Do not put the wrong type in, it is important you add the right color/type of anti-freeze. If not sure, just add water for now, and find out what kind to add later. Many anti freezes ARE NOT interchangeable.

basic things first, make sure your oil level is correct-any engine noises? If level is good, and no noises, consider getting an oil change done asap, and possibly with a slightly heavier oil-you left out important things, like what engine, how many miles, what oil in in it, how it runs now...all important information. It could be as simple as just needing an oil change or as involved as a new oil pump, or basic as a bad sender unit-more details, please...

it prob isnt the heater core usually when that goes u blow antifreeze steam into cab from heater vents. prob water pump or pin hole in radiator line if from the front of the engine or bad gaskets or bad freeze plugs if from the rear also check ur thermostat to make sure it working prop because u could simply be blowing out ur over flow line cause **** is plugged an over heating

Check your coolant level. It may be low.
Did they put the proper mixture of anti-freeze back in? I would have the anti-freeze checked. Or you can buy a simple little tool for a few bucks and do it yourself.

A radiator hose is supposed to be "hard" to withstand the heat. If hoses become soft it is time to replace them.

I don't know enough about Mercedes to answer your question much further other than to suggest the thermostat. If they put in a new radiator, they should have suggested putting in a new thermostat also, but they don't always do that.

Check your anti-freeze mixture first.

Simple things first.

Many believe that most brands will give you very similar protection. What is very important is that you are aware not to use full strength anti-freeze. You can buy pre-mixed if you don't want to mix the anti-freeze and water yourself.
Most recommend about 50% anti-freeze, and 50% water. be sure to check the instructions on the bottle.

I hope this helps you.

No, the tester lets you know if the antifreeze is strong enough to protect your engine. Just because you see it, don't mean it is not weak and needing to be replaced.

Its best to check when cold since heat makes fluid expand. Always use 50\50 mix.

Anti-freeze comes in different brands and longevity. This means that some do retain their quality for up to 50,000-miles, while others of lesser quality must be drained and recycled when they no longer protect the car's cooling system.
If you prefer a non-toxic anti-freeze for enviromental reasons, then you would pay more for that particular brand.
Some anti-freeze comes diluted 50/50 with water. However, most the important info to look for are all written on each brand, especially maximum freezing capability.
However, any anti-freeze capable of keeping its liquidity at minus 20-degree Farenhit would be a good for your car.
It is good practice to avoid contacting the car's body/paint with anti-freeze. Storing anti-freeze at a home dwelling is strictly discouraged.