Oh Kasey, sorry to hear about that. Being a human pin cushion stinks! What did he give you for the constipation?
This site explains your procedure very well. http://digestive.niddk.nih.gov/ddiseases/pubs/ercp/ The parts that you would have to do sound a lot like the prep for the upper and lower GI series. Honestly, the cleansing part was the only rough part. I suggest getting some nice soft TP before hand if you end up going for the procedure. When does he want you back for the lab results to decide on the procedure?