This video is pretty much what you have to do, but it is a lace piece:
https://m.youtube.com/watch?v=P0HyMTr4q50
Just start from the back of the unit, take it really easy and slowly, and use lots of solvent. If there is tape left on the unit when you get it off, give it a long soaking before you try to get it off.

You can cut the part of the base which has hair on it, but the hairline is usually made with a special graduated density for a more natural look, so you don't really want to cut that away. Why do you need to cut into the hair?

You can apply Got2B either to your scalp or the base. I find applying it to the base is easier. I probably use about a tablespoonful to my whole scalp. You want a layer about half a millimetre thick all over, if that makes any sense.

You can dye the unit, but it is quite tricky - not really something you want to undertake in your first few days. If it up just a red tone you can cure that with colour-correcting shampoo. Can you take a picture which shows the problem? Blank out your face, obviously.