Enclosed/Covered Porch Dilemma

We just purchased an 1870s brick and wood sided farmhouse in Southeastern Ontario, Canada, and had every intention on pulling the front porch out, and restoring it back to the covered porch (it was enclosed a number of years ago... and badly). Our issue is, we've started pulling it apart and discovered that when they enclosed the porch, they rebuilt it... but what they have done is built the posts on top of the rotting OSB flooring, now I understand that we will need to jack up the porch roof, and then knock out the posts, however we will also be needing to remove the support beam that runs the length of the porch, and the shorter one at the one end of it, My issue is that I don't know how I would go about integrating a new beam into the original structure without pulling out the roof, unfortunately the old beam is unuseable because when putting in the enclosed portion, they knotched out the support beam, so in essence it's carrying a lot of weight with a massive knotch taken out of it. If you have any suggestions, please help! ... Also, we "discovered," or more like knew we had a mouse infestation or did... anyway, when we pulled out the suspended ceiling we found that they had insulated, and vapour barried the ceiling... our issue? mice have made a nest in the insulation, we want to take it out and put a new ceiling in and were wondering what sort of "gear," we should wear... masks, etc we should buy in order to do this. Since it's summer, the mice are out in the fields and the barn... so we're not worried about mice falling about all over the place, and also should we put some mouse poison in the ceiling when we put the new ceiling up? or no? Thoughts and suggestions would be much appreciated.

I'd wear a dust mask at the minimum to avoid breathing mouse feces. Mouse poison is a good idea but, it will be stale by the time the mouse return for some indoor comfort. Sounds like a sizeable job, post some pics and we can advise you better.