Informed consent. Talk to your doc. At the least, you need to know the nature of procedure, indication for it, alternatives to it (including not doing it), material risks, and expected benefits. Get brochure from md. Can get info online from GI organizations and medical societies.
First of need. To know where is it? Why is it being done and what prep is involved. You will likely need somone to pick you up. You need to know what to expect after the procedure and what are the risks involved. If you take blood thinners, you need to know when can you restart them. Youu wont be able to drink any alcohol for 24 hrs. All this needs to be discussed at the time of consent.