I just purchased a home and have a detached garage with 100 amp service... I want to put a pretty decent heater in the garage and I am considering buying a QMArk Heater (Electric). The model is a qmark MUH108, Volts A/C 60 Hz 208... Amp 0.6... Kilowatts 10... Phase 1/3...

If I purchase this heater will I be able to install it in the garage with 100 amp service with the correct breaker installed??

You can use a 10kW heater, but it will be hugely expensive to run, you know that right?
Also, that heater will not work. You need one that runs on 240V, not 208V.

That would be like running an electric oven--pulling over 40 amps.