Advice for apparent water damage in our garage

Hello all,

Just bought a new home that had a full inspection as well as disclosure, none of which found or indicated water damage. After a couple of days of living here, in better light, I noticed what appeared to be rot at the front corner of my garage adjacent to the third stall. A closer inspection seems to indicate water damage. The damage seems to start from partially up the side of the garage door, nothing from the ceiling or above the garage door indicates any type of past or current leak.

Wondering if this is something a carpenter could take care of, namely, cutting out the rot at the base, taking a look behind to see if this is an old or current problem, and then replacing the 2x4s and particle board?

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