........ Going to start on the headliner next. Never done before so this could be ugly.
But consider that your saving the cost of having it installed. You could go through a number of headliners and still come out ahead cost wise.
And your learning a skill that you can apply again at a later date, apply to other owners cars, work out a trade for something you need done or a little pocket change to buy something you need for your project.
Acquire skills and information anywhere you can you never know how handy it will become in the years to follow
As for the headliner - good comments/tips so far. Get the headliner out of the box, lay it out somewhere warm for a while to reduce the folds. It helps if its a little warm but I don't think anyone is using heat anymore. Reproductions are too thin and heat (like a heat gun or hair drier) doesn't work on these like it did on cloth headliners. Different tricks for different materials