you have a lot of questions... I would recommend taking some kind of class or reading some books to help you understand how film works, how to use a 16mm camera, and how the workflow for film usually goes.
as far as your questions, here are my best answers:
First things first: DO NOT BUY AN ARRIFLEX...you will save way more money if you rent your film equipment, especially since film costs a lot more than miniDV, and you probably won't use it a whole bunch.
the arriflex s is a great camera for ameteur filmmakers, and it is powered by a motor which you may need to get separately. there are many motors you can get, each with different frame rates, etc. this motor probably requires an external power source such as a battery. Sometimes you can find a wall adapter. You should keep in mind that you cannot record dialogue at the same time as picture using this camera because it is much too loud. For Sync Dialogue work you may need to use an Eclair NPR/ACL, or an Arriflex BL (among other cameras).
as far as accesories, you will definately need a light meter, which allows you to set the the f/stop (t/stop) on the lens so that you expose the film correctly. You may also need extra lenses, which you should also rent.
converting film to a video format is called TELECINE. This is a service provided by film labs, and can get fairly expensive. The most useful digital formats that you can have film transfered to are (starting with most expensive and highest quality):
HDCAM
DIGIBETA
DVCAM
MINIDV
you can also get it transferred to BETACAM SP, which is usually considered higher quality than DVCAM or MINIDV, but is not digital. This means taht you would need digital dubs of the BETACAM SP tape for computer editing, but use the BETACAM tape as your master.
You can also have your footage transfered to a hard drive in a format such as DVCPROHD or uncompressed. You can also have it transferred uncompressed to a DVD as a .mov file, though this is not an option i recommend.
As far as other cameras, there are many other cameras out there, though i have to say that the easiest one to learn on is the Canon Scoopic. It takes only 100 foot rolls of film, but is so easy to load, and has an excellent viewfinder. Another option is the Bolex, and while it is slightly harder to load than the scoopic, it is a very common camera in low budger 16mm filmmaking. If you would like to see what can be done with a canon scoopic, i should have a film i made using one up in a week or two, so check back

If you want to just get more expreience using film, you might want to look into Super 8 film. It is the most idiot-proof film format out there, and while it is not the highest quality, it has a really unique look and helps you learn all about the workflows you can go through when using film.
hope that helped a little... Don't be too intimidated by film, because while it first may seem confusing, it really isn't any more confusing than video. it is just different.