For whatever it's worth, SAS defaults to 2,000 as a sample size in it's Graph Explore nodes. I know that this often produces graphs that are not representative in different ways. (SAS is top-of-the line data mining software.)
If you want a random sample in Excel, add a new column, put =rand() in the first cell, copy the cell down to the bottom; select all the data (all rows/columns), sort on the new column (direction doesn't matter), and select how ever many rows you want from the top going down.
I can't imagine trying to do exploratory analysis with Excel. Maybe there are functions I'm not aware of. How is it easier to find the standard deviation of 1,000 rows rather than the whole set? It's the same number of key strokes.
I would work with the whole data set.