@zahid
1) You can take both PIA and Qatarairways. I prefer qatarairways. They have good service and i have been using them for the past 2 years.
2) Why do you need to contact travel agent? For visa or ticket? If ticket, dont. Purchase on-line via credit card and you will find a cheaper option. If for visa then directly go and speak to qatar airways and request them to arrange a visa for you. You will have to travel with qatarairways in that case.
3) Hotels vary from 350Qr per night to 2500qr per night. (one QR = 23.5 pkr). You can find accommodation in SHEZAN hotel which should be economical but service is ordinary. If however you are asking qatarairways for visa and ticket, you may ask them to arrange accommodation for you in one of their hotels.
4) To move around, you can rely on the limo services offered by your hotel which will be expensive. Very expensive. The other option is local taxi service called "karwaa". They are not too many in number but still if you stand on the side of the road for few minutes you can find one. Their rate starts from 4Qr for first km and then i guess 1.15 qr for each subsequent km.
Hope it helps. I am in Qatar right now but will be leaving before Eid so wont be able to assist in person. Drop me a message if you need any further detail.
Adeel.