Garage Roof Replacement?

Hello chaps.

My garage was put up in about 1979 and used that great stuff corrugated asbestos concrete for the roof. Joy. We moved in about 2 years ago, and I'm noticing that when it rains, it tends to soak through, making things in the garage damp and musty. I think I need a new roof (or can it be repaired?) and be before I go out and hire in a costly contractor to do the job, I want to see if its feasible to do the job myself.

Firstly is taking the roofing panels off, and as long as I follow the proper procedures, like wearing a mask, keeping the panels whole, no power tools and double bagging the stuff for safe disposal in some council tip somewhere (I'll have to find that out), I think I should be okay with that.

What I'll be left with are those metal girders which I need to get stuff for and that's where I'm stuck. What do I use? Ideally I'd just prefer a corrugated plastic sheet to replace the roof with (this looks easy! ;-)) but will that do? Cost is a major consideration here.

Oh, and it's a double garage., and the slope on it is very slight (probably less than 5-10 degrees)

Any advice would be so much appreciated !

Paul H.