Ahhh - you've found the rub... People selling often haven't a clue what it is they're actually selling they just know that its "a bit odd".
The standard radio (Clarion) is a reversing camera, Minidisc player, CD-changer and radio, but I don't believe its a satnav. Once you've tried to manoeuvre in a tight space without the reversing camera you'll understand how important it is. The stanard radio will only be able to pick up Radio 2 unless it has a band expander fitted.
I believe the cambelt's not that big a deal and I've had mine checked and it was done not so long before I bought it.
I hope that's a bit more help,
Alan
(work's boring this afternoon...)