Large Barn Project

[Farmhand]

So I have barn project on a 70+ year old barn. It hasn’t been take great care of it. Most of it is in decent shape, but there are some trusses that definitely need to be replaced. As such, the roof line is a little wavey. In some places I’m sure the tin is what’s holding the roofline together. My question...would it be fine to carefully pull down any inside obstructions to the trusses and just do the repairs from the inside? Sister or temporary around any week spots. Being that I’m the only one around to do the work, I just don’t have the ability to take off the whole roof and do it at one time. Not to mention there is stuff in the barn.