1:25000 isn't used much. The standard topographical map is 1:50000 (terrängkartan), there are a few 1:100000 still in use, and the orienteering folks use 1:10000 or 1:15000 (at least they did last I checked), but those can be hard to track down and does not cover more than a few spots.
As to the grid; it is fairly simple; the main division is a km square, basically counted from the intersection of the prime meridian and the equator. You then get an X and Y (e.g. X=6589030, Y=1443339, sometimes the X and Y is omitted). It allows for arbitrary presicion, just add or subtract numbers on the end; 7 digits make for 1 m, 6 for 10 m, 5 for 100 m, etc). If you know two postiions you can easilly calculate the distance (unless you get into large enought distances that projection effects kick in).