how to install roof hatch?

[lilafter]

hi, i have a 2 storey home with low/no slope roof that has no roof access except via 2 storey ladder. those ladders are too heavy and scary for me to manage. want to have roof hatch installed before or as part of reroofing- tar/gravel removed and replaced with foam or single ply membrane.

so, my idea is to gain roof access via roof hatch. i have an access panel from second storey porch to low attic space. i've googled "roof hatch"- lots of options and many different price points... i'm small, for residential use, used infrequently for maintenence of roof, so i'm thinking to go for the 24x24 or 30x30 size wise. can anyone recommend a particular brand? seems all have insulation, made of steel or aluminum, hinged...they all look the same to me.

also, HOW does one actually install this? the only roofing quote i've gotten so far does not install roof hatches. i may have to hire this out separately? might it be a diy job? concerned about the weight of roof hatch >100 lbs and kind of support it will need.

thanks.