Replacing an exteriour basement access door

short background: our house is about 30 yrs old. The orginal door is in need of replacement.

I am most likely going to pick up a pre-hung, & have someone install it for us. Basically I am wondering how much "demolition" work should I expect from this and what is a reasonable "going rate" to have this work done. ( I have no objections to paying for quality craftsmanship)
I could throw up some pictures if this may help at all.

Thank you in advance
Mark