Answer: Without actually seeing the damage, I can only offer some educated guesses. Yellow spots can be the result of dog urine or a fungal infection. The odor you describe sounds like rotting roots, perhaps from poor drainage. If the soil isn't properly prepared before sod is installed, the roots won't penetrate into native soil. If there are low spots where excess water collects, the roots can suffocate (hence the rotten smell). It can be repaired, but it will be labor intensive. Repairing will involve rolling the sod up, rototilling the ground and then raking smooth the area; then re-installing the sod. Replacing the sod is an option, but if you have the sod replaced, you'll want to make sure the soil is properly prepared before new sod is installed. An alternative is to grow a groundcover that will take some foot traffic.
Best wishes with your project!
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