cracked drain pipe replacement

As I was replacing a leaky bathroom faucet in my recently purchased 40-yr old house, the drain pipe connecting the p-trap to the in-wall drain cracked due to corrosion. So I am left with about 5 inches of pipe to be replaced. There is a collar that looks like it can be unscrewed at the wall. Are these connections ususally soldered? Do I need to unscrew the collar or the pipe? I don't want to try unsrewing it and mess anything up.

The existing sink is wall mounted so all the drain pipes are chrome. I plan on installing a pedastal sink in the future. Any problems with replacing all drain pipes with PVC and connecting into the in-wall drain?

Thanks

It's probably a slip compression fitting. Loosen the big nut (you can unscrew it completely) and what's left should slid off of the stub in the wall. If there is a nut, it is not soldered. That nut compresses a gasket around the stub to make the seal. You can buy replacements in pvc or chrome plated copper.