Almost as much as they want. Attached to each C&M campus class is an instructor and an undergraduate class assistant. About 2/3 of the C&M class meetings are in labs in which the instructors and class assistants work one-on-one with their students. To get a consultation during lab time, all a student has to do it to raise a hand. Everyone gets to know each other in a way impossible in the lecture model of teaching, Frequently the friendships built in C&M extend way beyond C&M itself.
When I originally signed up to take C&M BioCalc for my freshman calculus course, my older brother tried to talk me out of it. He told me that I wouldn't learn anything, and that I would have trouble later on in my engineering classes. Out of stubbornness, I stuck with it. This past year, my brother came to me to ask my help. One of his mechanical engineering classes was filled with Calculus III material and he was having trouble. After I helped him, he said to me, "I wish I had taken a C&M course. I probably still would have forgotten all of the formulas, but at least I would know how to go about getting the answer."
Techs support both the lab machines and the software used in this program.
In the event of a problem, send an e-mail to tech@cm.math.uiuc.edu.