need some advice on roofing!

Its an 1822 house, so 190 years old, very small at 900 square foot. It has a cedar shingle roof, which appears to have reached the end of life, most of it is covered in moss, and other stuff, and its coming off.

I was doing some research, and if I buy this house, im going to have to replace the roof surface, and do some work on one wall. Price is right though, its on short sale and a steal.

Ill know more after a home inspection is done on all the house systems, but I can tell just from looking at it the roof will be needed soon.

My question is what are the different substrates between the cedar shingle, and the asphalt roof material? Whats the best way to get the shingles off? Ive been watching youtube videos, and think it looks straightforward, but any advice would be appreciated.

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