Welcome to the forums VOYUERS;
Obviously before you begin, make a back-up of the files listed below, so you don't irrevocably break anything.
Open your dosboxBlood.conf file with notepad, below [autoexec] (at the bottom of the file) comment out the imgmount line. ie: # imgmount D game.inst -t iso
If you want to keep the in game movies but kill the CD audio, you might be able to just mount the gog file by changing the above line to read "imgmout D game.gog -t iso".
If that does not work, you will need to mount your game.gog file as a CD image using a program like MagicDisc (or DOSBox itself), copy the Movie directory from the CD image into your Blood directory, and modify your Blood.ini file (again with notepad) to point to the Movie directory as it will be represented when in DOSBox. ie: "C:\movie\" rather than "D:\movie"
For online play, you will want to coordinate with some one to play against. There is the
YANG utility that helps facilitate connecting with each other, but you will still need to know about what time some one will be online. You can try firing up Yang, to see if anyone is idling, but don't be surprised if no one is there.