Hi,
The A and B Versions are LCD models, The C upwards models are LED.
A/B pricing around 350.
C upwards models are around 450 +
Ive bought 2 off ebay, had no problems, however if you want a new unit, There are members on here who can supply them. (Eddie_NL is the main man)
Stick with original VW.
Just Head unit is needed, straight plug and play and make sure it has the GPS antenna with it, Or one can be bought off ebay for under £20
You can get an MDI cable for the RNS unit, AUX and Ipod.
No need to upgrade speakers.
If you have an older canbus (pre2008 model Golf), you may have to update it, or make sure a modified Firmware is installed on it to prevent the battery from draining.
Hope that answers everything for you.
Raz