Suspension Issues - 2005 SL500

[bbarroninsc]

I'm having some suspension issues and thought I would toss this out there for an online opinion

2005 SL500 Around 75k Miles

History Of Trouble
1) Slight griding like noise coming from under car or tires while driving (is this even likely caused from suspension?)
2) Grinding noise gets worse, and even does it right after cranking when idling
3) ABC lights start to come on intermittently, with the last being the visit workshop one
4) Car begins to sag when not driven for a couple of days - sagging on passenger side


Codes From Indy
C1525
C1526

Repair Recommendations- Parts
1) Replace both front and rear hydraulic valve blocks
2) Some sort of hose kit for the rear? (is this necessary if I chose the older version of the valve blocks 2203200358 vs the newer one 2203201258?)

Does this sound like an appropriate diagnosis? I was told to seek a second opinion due to suggestion of needing both valve blocks, and because of the grinding noises.