before ur rp is stamped, u can get a temp qatar licence based on the saudi dl.
once ur rp is stamped in ur passport, u can apply for the permanent licence, valid for 5 years.
it depends on the officer if they will take ur saudi dl and give u a qatar dl.

i had a uae dl, i got a qatar dl without having to surrender the uae dl.
temp licence will cost u 150qar and is valid for a 1 month and renewable.
permament dl will cost u 250 qar