1a. http://reviews.cnet.com/network-storage/apple-time-capsule-500gb/4507-3382_7-32818588.html says it can connect to a PC as a NAS (network attached storage) either via USB or Ethernet. If it came with a user manual that's a good start to learn how it works.
1b. Any external disk is less reliable than an internal one. So while you could use this device to store movies and whatever other media you want to put on it, be sure to have a backup copy if you don't want to lose them.

2. If your PC has an HDMI output, all you've got to do (1) connect TV and PC using a HDMI-cable. Six meters might be rather long so better ask the shop where you buy that cable what they think of it ,(2) find out how to activate that HDMI output on your PC, and (3) find out how to choose the HDMI input on your TV.