you don't need the textbook. don't buy minitab either. you can use the program already downloaded on the mills computers.
the midterms were very similar to the practice tests at the end of the lab manual.
know how to do all the practice tests inside out, and you should do very well.
the lab manual is relatively cheap ~16 from the tank
p.s. the textbook was useful for the charts at the back of the book*
but Volterman provided pdf files of the charts on his class website
check it out:
*control f-"upoaded a chart for t quantiles" at the website
but these charts are available on the general web as well