P38 and D2 are both burdened with aging electronics, the P38 more so than the D2 (depending on how equipped).
If you replace the air suspension on the P38, the big issue is going to be the HVAC. blend doors, the control head, the heater core - all are going to give various problems. The rest of the systems actually hold up pretty well. I have a 2001 P38 that I am the original owner of. My greatest wish would be to switch the HVAC over to a lower spec manual control (found on Euro but never NAS models).