Assistant Commissioner Derek Byrne, who is in charge of the national support units, is heading up the massive investigation team based in Dundalk.
Senior officers said last night the aim was to build up a strong case against the prime suspects before making any significant arrests.
'Sunday Independent' journalist Guerin was shot dead by a drug trafficking gang on the Naas dual carriageway in June 1996 and several members of the gang were subsequently charged with serious offences and jailed.
Officers from all of the specialist units have been drafted into Dundalk to join local gardai and members of the national bureau of criminal investigation in the hunt.
One senior garda said: "We are in this for the long haul.
"A lot of work has yet to be done before we are satisfied we have the right people in our focus and when that is completed we will make our move."
The murder investigation is now being expanded to include a series of burglaries and robberies that have been carried out in the Cooley peninsula over the past couple of years.
Detectives will review the modus operandi of each crime to establish a pattern and determine which of them are linked.
They will also sift through the evidence gathered in the investigation of these crimes at the time they were committed and look for similarities.
"We plan to build up a profile of each of the suspects and compare it with the information that is currently being collected about last Friday's brutal murder," the officer said.
Although dissident republicans have not been ruled out, the investigation at the moment is concentrating largely on the members of a gang who are mainly from Dundalk but have been living in the south Armagh.
Many of the 15 to 20 strong gang are well known to the gardai and to the PSNI.
The PSNI, who will play an important part in the cross-Border investigation, had a number of senior representatives at yesteday's funeral.
A section of the investigation concerns the theft of the high-powered VW Passat used by the killers in their getaway.
Gardai believe the two-litre vehicle was stolen to order in Clogherhead, Co Louth, last Tuesday night or Wednesday morning.
Detectives will try to link the theft to similar crimes in the area to build up a picture of the thief.
Other members of the team are poring over CCTV images from around the Lordship credit union premises on the night of the murder.