If you did a Google search then you have probably gotten some good info on it.
My nearly 6 yr old ds is an SID kid. Depending on what senses are dsyfunctional then there are different symptoms, issues, and treatments.
My son was not diagnosed until he was 5 and although I knew in my gut that something was not quite "normal" with him, I knew nothing about sensory processing disorders so the past few months have been an incredible emotional rollercoaster as I quest to find answers to help my sweet little boy. I knew about the 5 senses but I had never heard of vestibular or proprioceptive senses. I did not understand how sensory disfunction explained why my son could not walk up stairs or catch and throw a ball. None of it made sense to me.
I wish more than anything I could walk around in my child's shoes for a few hours so I could understand how he experiences the world.
Some of the things that have helped me the most are these books that I highly (and I mean highly) recommend:
The Out of Sync Child by Carol Stock Kranowitz
Raising a Sensory Smart Child by Lindsey Biel
I also recommend the book Quirky Kids by Perri Klass MD.
My son has an "official" diagnosis of "Developmental Coordination Disorder" or Developmental Dsypraxia, once upon a time is was also know as "Clumsy Child Syndrome" his issues are mainly motor based sensory processing but he totally has other issues and like sensory dsyfunctional kids there are a lot of common threads regarding tolerance, sensitivity/defensiveness to noises, variability, social issues, etc. My son also has some poor speech and language issues mainly due to poor motor control and articulation. He constantly walks around on his tip toes. On the other hand he is very, very bright and has tested at nearly a 12 yr old age equiv. on some cognitive tests. He is very loving and has an incredible imagination. He is one quirky little dude.
There is so much that can be done to help kids with these issues - the first step is to understand the condition (which is a lot to understand) and then to narrow down the issues that are specific to the individual and then to work to help them. Early intervention is key and can make a world of difference! Best wishes to you and your family!

sorry for such a long post!