Captain reported the PFD malfunctioned during an ILS approach to AVP airport. While attempting to resolve the issue; the flight crew received and responded to a terrain warning. Captain cited an incorrect altitude selection and possible 5G interference as contributing factors.

Narrative

We were cleared to HEAPP intersection; cleared ILS 4. I was waiting for the ghost needles to appear on the PFD's to indicate the approach course for the ILS. It never did so I selected HDG mode; switched to the ILS frequency then selected green needles. This process was attempted a number times as the selected mode on the control panel did not match the PFD FMA mode. Also once green needles were selected; the ILS course had to be selected as well. After a couple of calls from Wilkes Barre Approach had distracted our attempts to resolve the anomaly; I was considering discontinuing the approach as I was becoming task saturated with the inability of the flight mode control panel to present the selected mode in the PFD FMA. This was about the time we got the terrain warning. I responded to the terrain warning as I had the terrain on my side in sight and the First Officer said he had the towers in sight. Not sure if the terrain warning was for the terrain or the towers and I do not recall what our altitude was. Also due to the glare reflecting on parts of my MFD and PFD I was not able to clearly see the approaching terrain depiction until the terrain aural warnings sounded. As I initiated an immediate climb the terrain aural warning ceased and the very small terrain depiction disappeared from my MFD.The NOTAMs indicated the GS for ILS 4 was out of service so we had originally planned for the RNAV 04.I had sent an ACARS (I think about XX minutes out) requesting the current METAR; this indicated that the CIG was going to be below the adjusted minimum for the RNAV 04 approach which had been originally planned on and loaded in the FMS. We were discussing changing it to the ILS 04 with Glide Slope inoperative as the minimums were lower than the RNAV or requesting the ILS 22. As we were getting closer to AVP we were beginning to receive parts of the ATIS which indicated the ILS 04 was in use. Once the decision was made to made to load ILS 04 into the FMS; our time remaining to brief the approach and complete the descent checklist was somewhat compressed. As this airport is NOTAMed a 5G airport causing the radar altimeter to become unreliable; my concern is that this could have been a contributing factor. At some point approaching JISAG (the final approach fix); I must have selected a lower altitude and must have inadvertently initiated a descent before I had intended to.Should have discontinued the approach and requested vectors to the final approach course. Perhaps Wilkes Barre Approach should be made aware of the poor reception of the ATIS broadcast on the LVZ VOR. Also this approach should be issued or accepted only by vectors to intercept the localizer outside of HEAPP intersection and not a 30 degree intercept to the localizer. This aircrossing HEAPP intersection is where the obstacles are located and this could easily happen again if the auto tuning function fails.Due to the ATIS being broadcast on the Wilkes Barre LVZ VOR; it had to be manually selected to receive the ATIS. The reception was poor and it had to be listened to a number of times to hear it in its entirety. Once the ATIS was obtained the AUTO function was reselected on both NAV 1 and 2. However it must not have taken as the ghost needles on each PFD were never presented. At some point approaching JISAG (the final approach fix); I must have selected a lower altitude and must have inadvertently initiated a descent before I had intended to. Not sure if Wilkes Barre Approach is aware that the ATIS broadcast on the LVZ VOR is not easy to hear in the best of conditions. Also as this airport is NOTAMed as an airport where the radar altimeter maybe unreliable whether or not this could also have been a contributing factor.