A Mechanic reports the lack of adequate documentation between Avionic's personnel and Mechanics; along with limited training and inadequate Maintenance procedures thatled to the Internal Compensation Unit (ICU) not being moved from the removed AHRS unit to the new installed AHRS on a Saab SF-340.

Narrative

March 2009; we were waiting for an Aircraft On Ground (AOG) Attitude Heading Reference System (AHARS) computer for the #2 system; after already replacing the #1 AHARS and completing all check functions. The AOG part arrived in the morning and was quickly installed so we could do the required swings. After completing the swings; both left and right AHARS were exactly the same. There were no Avionics Technicians available; so Maintenance had to install the AHARS #2 computer ourselves. I don't remember if I was the one to install it or if I had one of my newer Mechanics do it; but I was the one who signed it off; so I am responsible for it. Since we were unfamiliar with the AHARS computer and rushed to get the aircraft to the gate; the step to move the Internal Compensation Unit (ICU) from the removed AHARS computer to the new AHARS computer was missed. I was notified by a fellow Maintenance person who had heard about the incident.I think this event occurred; because of not having qualified Avionic personnel on duty; who were familiar with the system; and also because of the rush to make flight times in the morning; caused the step in the manual to be missed. Everything seemed OK at the time; since we were not previously aware of the requirement to move the ICU from one AHARS computer to the next; there didn't seem to be anything wrong at the time.With having many new Mechanics working; I sometimes get task saturated and the the more last minute things to deal with at the end of the night; the higher the risk of unintentional error gets. I talked to a Supervisor in the morning who was Avionics qualified; and he did not bring it up as an unusual step to be aware of; to make sure no errors were made. It remains my fault however; as my name is on the paperwork. The ICU was installed on the aircraft; Operational checks completed and aircraft released for service. It would be a good idea; if Mechanics are expected to work on Avionics tasks; that we are given some kind of training on things that are out of the ordinary; such as yellow tagged parts missing ICU's that need to be moved over.When the base task is; Remove and Replace (R/R) the computer; the secondary task of moving the ICU could be and was missed. If someone had made an issue of this step on the paperwork that was left; it would have helped a lot. What would seem adequate documentation from one Avionics person to another is not always adequate from a Avionics person to a Mechanic; as we do not usually work on those systems.