Ok some of the MD's I am looking at say this ,IN: line/optical no microphone input. Can you plug a mic into this or no? I was told as long as it has a line in it is fine, but I want to make sure. Is there any benefits/disadvantages or extra equiptment needed(if no mic in) to either way?
The headphone socket is the line out, so don't worry about that, all MD's will have one. Don't bother with mic in, all you need is line in.
Unless you're recording quiet acoustic stuff, likelihood is you'll overload the recording on mic-in. This is why everyone is suggesting all you need is line-in.
Edit: With a minidisc (or most other equipment) recording line in, you also need: mics and battery box, not just the mics. Again, look into a second hand Nomad JB3, its a bit better than minidisc and much easier to transfer recordings onto your computer.
I do understand the uncertainty with dropping dollars on equipment, but the way to do this is download or trade for some shows recorded with stealth equipment (with known equipment lineage), and buy what you like the sound of.
However there's already enough information in this thread, let alone the links given you to enable you to choose something sensible, and hopefully to your budget.
Good luck!
Humbug