The Qatari Riyal is pegged to the US Dollar

Buying 1 USD u need Qrs.3.65
Selling 1 USD gets u Qrs.3.64
at any of the Exchange houses. like Al Fardan, Gulf Exchange or any exchange house, you will need your original passport

Banks charge an additional fee, you will need proof of ID (passport)

Carry about USD 500/- (and exchange at the exchange house) for a week, depending on your spending habits. You will need the cash to pay at the smaller shops, all foreign clothing stores, supermarkets, hyper markets will accept the dollar or credit card.

Most companies provide an advance (at least if you ask) so if you want to save on your credit card exchange charges, bring cash to last you a month or less (USD 1,000).

Safe journey, dont worry too much. Most people here are kind and you can be sure, your colleagues will help out.