looking to buy - 91 gl

hey guys whats up, ive got a couple questions for ya and maybe you can throw some info my way.

Where can i find a headliner online, or for a good price for that matter?

how easy is it to swap a manual transmission in? cost?

i was told the sunroofs are a common failure, any fixes i should know about?

there was a small electrical fire near the steering wheel, and the car looked like it had an aftermarket stereo. it looked like a green wire coming out of the steering wheel shorted to a green w/ black stripe one and melted some of the insulation off... any insight?