thanks Pamela!
I used the plane many years ago from Rantepao -- very scenic but unreliable and expensive (I think it did not run for years at one time). Also max 10kg free luggage.
Take the bus -- Litha is good in the morning but goes at 10:00 sharp (not jam karet) and you can see the scenery that way. I have not travelled at night. depending on the timetable I think you will have to spend a night in Makassar. Last time (in Jan 2007) I stayed at Hotel Surya Berlian which was reasonable and convenient. (OK there was no water one day and the breakfasts were not very nice.) Convenient (especially by becak) to the sights in Makassar, internet and airline offices. (You will need a taxi to and from the airport and bus station.)
When you get to Rantepao the bus will take you to your hotel (so choose one in advance). I stayed at Maria last time but have stayed at Duta 88, Wisma Monton, Pia's Poppies and Hotel Pison previously and liked them. (I also stayed at Imanuel and could not get out fast enough.) Guides will find you quickly enough.
Paul