the V8 fruit juices are a life saver in our house! Take lots of notes including thinking back over the past 10 years. If they do the eval right they will ask about a lot of history. I am aspergers who is very sensitive to sensory things like textures and tags. If socks are an issue turn them inside out. My son is autistic but has fewer sensory issues. the more specific you can be about what your son struggles with the more I may be able to offer.
There are a lot of things you can do at home. The tools that are marketed for autism are often very expensive but I would be happy to help you with affordable alternatives if something is suggested.
My favorite thing is my weighted vest when I get overwhelmed (you can google OT vest. The others are not as good in my experience).
anyway... I work in the field but not a Dr,.OT or speach therapist...just someone with a lot of experience so feel free to ask away!