Yeah, what walker machine do you have?  Hard to imagine a 9600 having only 1600 sep hrs.

 No matter the model, if I were you, I would do as much repair as I could myself!  Taking it to dealer is OH so easy, until you get the bill.  If you have just recently done cyl bars, then you're bound to be mechanically inclined.

If youre going to trade it, then it would not make sense to get the machine in perfect condition (because you wouldnt get all your money back), but I personally think you would be ahead to get some of the bigger issues taken care of.  For instance, if you were to try to trade it in, and the brakes did not work, you would get nailed for that one.  Dealer always has to assume worst case scenario when estimating how much it's going to take to fix the problem. It could be something as simple as fluid level, air in the line, or master cylinder (the brake problem). As far as wear on the augers and chains, it really depends on just how bad things are. From the info you told, I would prolly suggest replacing the items that are worn excessively if you are going to keep the combine, and not replace these items if you are going to trade it in.   Only you can answer the question about trading, as only you know the amount of acres it needs to harvest, crops harvested, hrs/yr put on the machine, etc..... and your financial condition.