Sync between Classic iPod and iTunes (10.5.3)

Question

I do hope someone may be able to help me to sort out a mess I've got myself into concerning the transfer of music from iTunes to iPod, and back again. I don't know how it happened, but every attempt I try to untangle things, it only seems to make the problem worse.
Here's what's happening:
1. I have an older list of playlists on my iPod, which I want to update heavily (with the replacement tunes coming from my iTunes playlists);
2. at the same time, the up to date set of playlists on my iTunes I want to transfer to my iPod;
3. unfortunately, one playlist (though still in iPod), has completely disappeared from the iTunes. A complete mystery.
4. the Devices tab down the left hand side seems to come and go at will, depending on whether the iPod and computer are connected via a USB. Is that normal?
So, could I receive the help and advice of Forum members to:
1. transfer songs from the iTunes playlists to my iPod music playlists;
2. get rid of the older playlists currently on my iPod - with the exception of one playlist (see point. 3 above); and
3. advise about the ever-disappearing Devices tab!
I look forward very much to receiving the help from any Forum members. I should add that my computer skills are pretty much in the 0-5 bracket, so replies in simple English would be much preferred. Thank you.

Answer 1

(b) However, there are quite a number of music categories which I don't really want. i.e. Cover Flow, Artists, Albums, Compilations, ?Songs, Genres, Composers. Grateful advice whether I really should keep these lists: I can't see the need for them, though.
(c) In addition, I wonder if you think I need to retain another category of tools in my iPod: i.e. Videos, Photos, Podcasts. What do you think?
I don't believe those can be removed as they are built in to the iPod's software unforunately.
2. iTunes:
(a) By some means unknown to me, my iTunes pages seem to have sorted themselves out roughly. In other words, I have a coherent single Playlist which lists in order some 11 separate catergories of music, as well as the odd "iTunes DJ", whatever that does!
I'm a litte lost on this one.  You should be able to view all of your music stored in iTunes by clicking on the Music category at the very top under Library in the left hand pane of iTunes.  It sounds like you are referring to the playlists section in the left hand pane of iTunes.  ???
I guess the other point to mention belatedly is that my name, under "Devices", only appears after I conect the iPod to the computer's USB. We live and learn!
That's how it is intended to work. Your iPod will only be listed in iTunes when you have it physically connected to a USB port on your PC.  This allows iTunes to communicate with the iPod.  You can not edit sync settings for the iPod when it is not physically plugged in and appearing in iTunes.
Hope this clarifies at least a few of your questions!
B-rock