Gear box info please

Hi, I am running a 02 tdi L+ K 110 Estate with 174,000 on the clock. How slack should the gear change be, compared to other cars i have driven it feels fairly loose. How often should the oil be changed, will this change the way it feels,and how easy is it to do yourself are there any photo's around to show the drain / filling plugs. I would probally get the oil from the dealers is this the best value for money.