fermentation temperature

This is my first time brewing a lager. This question probably applies to both ale and lagers. How important is it to worry about fluctuation in temperature? Is a 5 degree change a big deal? I'm using white labs pilsner lager and it says optimum fermentation temp is 55 degree, but I notice other people fermenting as low as 48. I was reading for a diacetyl rest I should bring the temp up to 60. but this seems like a minor change from 55. Is it find to bring up the temps to 75? These questions probably aren't ordered the best way, but any resposne is appreciated. Thanks

If you are lagering, you do not want the temp at 75 (you don't really want it there for ales either). I think 55 is good, but not sure about the 60 or 48 parts. I will let someone else answer those.