Well if you intend to output to mp3 it is rather pointless to worry so much about quality of cables and connections and such.

You can either output the headphone socket on your hi-fi into your soundcard, or perhaps directly connect your turntable using the standard red/white audio cables, depending of course on your soundcard and if your turntable has a pre-amp.

In terms of the actual recording, if you do only want MP3 probably best to use 44.1khz 16-bit Stereo, or if you want to keep it on proper CD you could record at 48khz or higher (if possible) and downsample after you have removed the hiss, pops and clicks.