3 year old son, waiting for diagnosis for ASD

I want to introduce myself as I am very keen to have support and advice. At the end of the summer term the nursery my 3 year old son attends raised concerns about his behaviour. He has repetitive thoughts, interests and behaviours and does not interact with his peers, but likes adult company. Initially I was in denial, however what I thought were some of his quirks I realise are signs of ASD. He's fasinated by washing machines and fans and flaps his arms if he is excited or stressed.  If he ever goes into somebody's house the first thing he asks is where is the washing machine, although he doesn't have to see it, he then goes on to find the toys. He speech is good, although a two way conversation doesn't really happen. He knows plenty of words and can say 5 words in a go. Just recently he has successfully been toilet trained and is dry at night. We are due to see a developmental paediatrician but not till November and from what I understand an exact diagnosis will take a number of months to receive. I keep hearing that early intervention is key but I'm not sure where to start. Could anyone explains what happens post diagnosis? I want to start helping him now, I have read about different therapies but am feeling overwhelmed. Also, does anyone reading this thinks this sounds like aspergers? My son starts pre school in a couple of weeks and I want to ensure he receives the support he needs.