Just go to
http://www.dd-wrt.com/site/support/router-database
put in "WRT610N"
There are 2 revisions, 1 and 2, just find which yours is, download the build, install it to the router (its as simple as that)
The adding the code, is literally copying and pasting a line of code to a text box on the router and clicking save, nothing exciting
and as you say....
"If it aint broke, modify and make it better"