I am wondering why you are thinking about weaning so early. Babies need breast milk or formula until they are a year old (at least). You are already nursing, and it is free and the healthiest choice, so why quit so soon? You are already over the nursing hump- it is all easy from here.
Are you wanting to wean because of a job or to take a night off? For just a few hours save his solid food time until you are gone and leave the sitter with a bottle and a spoon, just in case.
To answer your original question- weaning. To do it as painless as possible, for both of you, you have to get him used to the bottle first- if you can pump breastmilk into it that would help with the transition, but if you can't (I never was able to pump) that is ok too. Find someone else to give him the bottle the first few times without you around. You will have to leave for a few hours, or else he is just going to cry until you give in and nurse him. Get him to drink one bottle (or at least out of the bottle) everyday for a several days and then offer it to him yourself. This might be a slow process, but your breastmilk doesn't dry up overnight anyways, so while you are weaning him you will be cutting down on your production also- less pain for both of you.
Good luck. And please know- there is nothing wrong with nursing past 6 months if you and your son are happy.
EDIT TO ADD OTHER QUESTION:
He does need to be fed at night time. Breast milk digests easily and quickly and so their hunger comes back frequently.
You are not alone- a lot of moms who breastfeed struggle with the same questions you are asking- "am I nursing too long?" "should they be sleeping more" and "should I have let him sleep with me." Let me tell you from experience that it ALL works out. Both of my sons co-slept, both of them kept me up at night, both made me wonder if I was doing the right thing. But in the end I know that I did the absolute best for them, and now- years later (4 and 8) they are happy, healthy, sleeping in their own beds (which the transition to was SO easy- we just skipped the crib entirely and when they were old enough to safely sleep in a big boy bed by themselves they were excited) and the struggles of early babyhood are a distant memory. You will eventually get sleep- there is no need to rush anything now.
Don't let anyone ever tell you that breastfeeding or cosleeping create a "bad habit." Both are healthy, both give your child security and emotional bonds. So snuggle that baby, nurse that baby, love him and relax. It is all good.