UNFAMILIARITY WITH ILS SWITCHING PANEL.

Narrative

I WAS WORKING THE LCL (TWR) POS WHEN AN ACR X FLT DEPARTED GEG TO PDX; IFR. AFTER ACR X CONTACTED DEP RADAR; DEP RADAR CTLR ADVISED ME VIA LANDLINE THAT ACR X (WHO DEPARTED RWY 21) HAS AN INFLT 'SIT' AND NEEDS TO RETURN ASAP VIA COURSE REVERSAL; FLY THE ILS TO RWY 3 AND LAND. WITHIN THE LAST FEW DAYS; HOWEVER; FAA TECHNICIANS HAD INSTALLED A NEW (AND COMPLETELY DIFFERENT) ILS MONITOR AND SWITCHING PANEL IN THE TWR CAB; AND MYSELF OR OTHER 2 CTLRS ALSO IN THE CAB HAD NOT BEEN BRIEFED OR TRAINED ON ITS OP. THUS; FOR A SHORT PERIOD OF TIME; I WAS NOT ABLE TO CHANGE THE LOC FROM RWY 21 TO RWY 03 TO ACCOMMODATE THE IMMEDIATE REQUEST OF THE PLT. I ADVISED THE RADAR CTLR OF THE SIT; AND LUCKILY; HE HAD OVERHEARD HOW TO SELECT LOCS. HE GAVE ME INSTRUCTIONS; I CHANGED THE LOC VERY SHORTLY THEREAFTER; WITH THE ACR FLT AT THE FINAL APCH FIX FOR THE ILS. THE ACFT'S L ENG NACELLE HAD COME LOOSE; AND THE PLT FEARED AN INFLT LOSS OF THE NACELLE AND/OR OTHER COMPLICATIONS. THIS CRITICAL SIT COULD HAVE BEEN AVOIDED IF FAA TECHNICIANS HAD BRIEFED CTLRS PRIOR TO THE NEW TWR MONITOR BEING INSTALLED. HOWEVER; IT'S 'BUSINESS AS USUAL' AROUND HERE; AND HAS BEEN FOR A LONG TIME!!!