You still need to worry about the crown to axle measurement to closely match your old fork. so yeah, the difference in length matters a bit. But a slight difference isn't going to be a huge deal. Chances are it will just make your head tube angle steeper and you'll get faster, more responsive handling (some people say twitchy). This could be a plus or negative. If your frame wasn't a pure race bike or track bike, chances are the headset angle isn't all that steep to begin with so this shouldn't be a big issue.

Head Angle of 73 degrees is considered ideal for some builders. 72 or 74 degrees is perfectly acceptable. You will notice a difference if you go from say 73 to 75 degrees or 73 to 71. This is for road bike geometry. Mountain bike geometry is a more relaxed to add stability.