What's the best way to connect my PC to the TV? Will using a
D Sub cable be OK? Or  do I have to use an HDMI/DVI cable which is more expensive. Further, do I have to disconnect my monitor while using the TV?

Bubblehead

If the TV has a DVI or HDMI input and its manual specifies that input a PC Compliant I would use those over a DSUB VGA

The VGA input is low res analog where the DVI or HDMI ports are high res digital

Samsung TVs usually specify their HDMI PORT 2 only for PC connection with TVs that have 2 or more HDMI inputs

Check the TV manual carefully

Although the VGA input can be used the visual result is always better on a digital input such as DVI or HDMI

use the digital coaxial or digital optical out to the TV

HDMI send sound to the TV through the HDMI cable from the video card

but you must hook up the SPDIF audio jumper to the video card if that video card supports HDMI. If the cards do not support HDMI OUT then you must run audio from the audio ports to the TV

Samsung TVs require HDMI PORT2 be used for computer input

If you do not use HDMI and the Samsung TV does not have a DVI connector then you must use the VGA instead

As for audio as mentioned, digital out from the back of the tower to the digital in on the TV is the best sound. If you do not have a digital in port on the TV for audio then you must use the analog output from the computer instead. LINE OUT will work but that is not a amplified output nor is it surround or anything like that. Its designed to be sent to a device that will amplify the signal on its own.

Your motherboard manual and your TV manual should cover all this in their instructions