One is the external chain from the outside port on the scsi card. The other in the internal chain, connected from the card's internal SCSI port. Typically, samplers should be put at the end of the external chain, because often they only have one connector, so you can't connect beyond that. Termination tells the Master device that the end of the chain is reached so it can stop sending commands. If termination is not set, when the master does not receive the acknowledgment from the last device, it might simply wait for it.
Termination is set on most devices by either a jumper or a dip switch, much like IDs.
Again this is easy. Just look for the termination diagram in the manual and do the jumper thing again. There's no soldering, wires, or mess. Just stick the little plastic jumper, a small rectangular plastic piece with two holes, over the correct pins. You can do it by hand alone, though sometimes a needle nose pliers helps pull them out them from their current locations, or put the girlfriend's fingernails to work.