interview dilemma

i got selected as an accountant in one of the schools that teach up to 12 . its government position but mine is not temporary for now . they are supposed to give me an appointment after 7 days of joining as trainee ,in the final date of the previous employee . i go there for 3 days after that for 3 days its leave . i am going directly on monday now. on tuesday they are supposed to give me appointment letter but i am not learning anything as only one previous accountant is busy . in between before these job vacancy i have given exam as an accountant in another college level communities campus that teach bachelor level. i passed it and my interview is on friday . i want to give interview and select between both if i cleared it . is it right decision ? If my first job gives me an appointment letter can i leave within a few days ??