2002 MPV DTC PO171, PO174 codes

After a non-blinking "check engine" light, my 2002 MPV van (66,000 mi) registered "too lean" codes DTC PO171 and DTC PO 174. After several vaccum leaks were fixed and fuel pressure checked, the "check engine" light reappeared after about 10 miles of driving. Van runs slightly rough. Mechanic said next step would be compression check, coil(s) check, and "major tune up", and he says substantial work just to get to the spark plugs. Does this make sense?

Thanks for suggestions!

Are the codes for the reappearance of the CEL the same codes as the original scan? If so I don't see any reason to worry about compression, coils, plugs..just yet. Sounds more like a faulty O2 sensor.