The SA-10 Grumble is a three part system that include a search radar, a tracking radar, and a launcher. It has an effective range of over 25 nautical, a ceiling of almost 100,000 feet, and a powerful low-altitude tracking radar that is effective at almost 0 AGL. This makes it effective against even the maximum specifications of the A-10. In short, if you see this thing, you probably need to just turn around.
SAM SA-10 S-300PS SR 64H6E
SAM SA-10 S-300PS SR 5N66M
SAM SA-10 S-300PS TR 30N6
SAM SA-10 S-300PS LN 5P85C / SAM SA-10 S-300PS LN 5P85D
SAM SA-10 S-300PS CP 54K6
You really should just call in SEAD if available to take out the SA-10, it's a threat even against aircraft equipped with HARM missiles in many situations.
If you absolutely must take out the SA-10 with your A-10 you need to be able to use the terrain to mask yourself until you come within AGM range. Set a mark point on the target beforehand, and track on it as soon as you emerge from the terrain for your attack.
You will most likely encounter triple-A and short range manpads when you do this, considering the high value of the SA-10 system.
Just keep in mind if you screw up this thing will kill up to 12 aircraft in around 36 seconds.
The addition of the S-300PS 64H6E SR unit to the group will allow the site to intercept incoming missiles.