The # hours / week of work depends entirely on your work ethic and your team's ethic. It could be 0 hours (if you're a leech) or 6 (if you're not a terrible person). Three experiments, each taking four weeks. The TAs don't know how to grade and will take off points for odd reasons, but it doesn't matter because you'll get a B+ or A- on average.

Definitely coordinate with your friends as to what day you'll be taking the lab, otherwise you'll hate your team and do all the work.