Flying air Canada to Beijing then air China to Sydney. Do we need to collect our checked luggage

I have an 8 hour layover in PEK, arriving at 5pm time. I understand it is possible to hire a tour guide for airport pick up and drop off. The company advertises night time tour with an English speaking guide for a 4 hour tour of local highlights. Are these safe and are the tour companies you recommend? Is there enough time to do this. Is a visa necessary?