Yes, you'll need new gaskets when reinstalling the EGR valve controller after cleaning. The EGR valve assembly typically uses O-rings and metal gaskets that should be replaced during any disassembly to prevent vacuum leaks.
Engine replacement for Thor Challenger runs 8000-15000 complete. Jasper or Ford reman engines recommended. Get experienced RV shop quotes.
Contact Gregory Poole CAT dealer for mobile service in eastern NC. CEL after battery failure often requires code clearing with CAT ET software. May be stored codes from voltage event. Engine running smooth means likely safe to drive to service if needed.
Multiple DEF codes typically indicate either a failing DEF head assembly or wiring harness issues. Professional diagnosis is recommended as DEF system tampering violates federal emissions regulations.