> What should the average salary expectation be for an Project IT/
> Office Manager be?

If you come from a high-tax economy, a good salary is probably the same as in your own country. Of course, because there's no personal taxation, your take-home pay will be much greater.

> How much would the above cars cost per month on repayments?
> Or where could i research this?

You won't be able to buy a car until you have residency, which might take a while. Expect to pay 2000QAR/month to rent a small family car.

> What are the school systems like for Expats? I have 1 child who
> is currently in his first year of school(He is 6 and a half)

You need to make a choice - British or US curriculum. To get your kid into a decent school next academic year, you need to apply now:
http://www.dess.org/Structure/s01_frames.htm
http://www.dohacollege.com/p_index.htm
http://www.asd.edu.qa/