Sounds like a fun trip (of course, you're missing the best part by not coming to the west coast ).
As others have mentioned, I would rethink the drive to Uluru. It's a very long way with very long stretches with literally nothing to see. If you can fly to Alice Springs and drive from there you'll save a lot of time. Make sure you take crocodile warnings very seriously and if you're camping in the NT you need to camp well away from water sources. Whenever you travel anywhere off the main routes in the NT you need to make sure you have plenty of water and supplies and it's a good idea to notify police of your intended route and arrival date.
Melbourne is one of my favourite cities and the restaurants are great. Avoid eating in Lygon Street. It's a tourist trap and the food is nowhere near as good as you can get in nearby areas such as Brunswick Street. It's quite fun to walk along there at night though. The city centre has great places for breakfast and fantastic coffee shops. There are also lots of nice wine bars along the river (Southbank side mainly) which are a nice spot to watch the world go by.
We only really tip at restuarants (not buffets) and even then it isn't a requirement. You might round up a taxi fare but again it isn't required.
No no no. If you eat in Lygon Street, please eat at Papa Gino's.
The best restaurant in Melbourne, in my opinion.
Everything else I agree with.
Brunswick Street is amazing, but Lygon street has some pretty good restaurants too. It does get frustrating having everybody try to get you to come inside and eat at *their* restaurant, but you can find a great meal that way. Brunswick street, though I love it, does attract a lot of hipsters. If you do find yourself in that part of town (and you REALLY should), try the Veggie Bar on Brunswick st. Makes me hungry just thinking about it. Have a cocktail at Polly afterwards.
There's a lot of artists markets around Melbourne on weekends too. You can pick up some lovely items if you're patient...
As far as the Great Ocean Road goes, Apollo Bay is beautiful and backs onto the Grampians. Good for beach access and forrest access.
Are you staying in backpackers or what, OP?