Fokkerdriver,
Pilots going straight from their ab-initio training to a B737 type rating course can, and many do, perform well throughout the course and finish it off with a satisfactory skill test.
Pilots with adequate experience, whom you would expect to perform well, can have problems with a course like this.
What I am trying to say is that it is very individual how a pilot performs during a type rating course. The combination of flying skills (in all its aspects), attitude towards the task at hand plus his/her motivation (which you would think is 110% for a selfsponsored individual) will determine (to a certain extend) the result of the course.
The "hairy experience", as you put it, is to understand that by going for, and becoming a pilot on a medium to heavy size jet, requires that you understand that to occupy the "office" in the front end of a 60+ tons airliner you have to be a cockpit professional. Lowtimer or experienced...........as long as you have the right attitude with a focus on the goal ahead you should be ok.