If you follow Dr. Schulze 's instructions exactly you shouldn't have any trouble with the enemas. There's really nothing to fear.
You can start the cold sheet treatment any time. It's nothing like a sauna. The IP recommends doing it once a week for a month and then less often after that. I was a chicken and only did it once.
I really, really recommend doing these with someone else present. First, you need someone who will keep you in the bath tub when it gets so hot. Second, you might feel like fainting while you're in the tub. You may also start to have heart palpitations. You may feel very weak when you need to get out and you may not be able to- that was my experience. You need someone to help you get wrapped up into the cold sheet and tuck you into bed. You won't feel like doing this yourself.
Everything you need to know is written in Dr. S's There Are No Incurable Diseases book which comes with the IP program if you order it from his website.