id say depends on how clean it is, auto is less desirable so would not be worth as much as a manual, but judging by your pictures the car is clean enough, id say it be worth around the 3k mark or over, as it is 2003, and so little miles. although this is a rough guess and i have not been looking at prices over the last year since i got mine lol.
the standard oem stereo are known to be faulty, this is very common problem but they can be got on ebay etc from time to time, although i would just put in a new double din or something.
im not sure about an auto but my manual averages 25mpg, when cruising on a motorway at a steady speed the mpg's says its doing a clean 40mpg, but the minute i put the foot down even just a little it shoots down to about 20 mpg lol, or another way to look at is i put in 40 quid a week and average 150 miles, she can be thirsty but in my eyes its worth it as it such a sexy car to drive lol
id say the car is nice, looks clean enough, and nice mileage on it, auto would not be my thing but everyone has thier own preferences i suppose, cream interior is pimp but might be hard to look after or keep clean.
welcome to the forum anyways and hope you end up getting the car, i love mine, smooth car to drive and reliable, starts every time
ps your golf is class, lovely car you got there, looks mint B)