The effort is considerably more than slight. Most of the advice on making a networked storage device such as the DNS323 results in what appears to be a functional Time Capsule equivalent, but they are lacking SIGNIFICANT underlying enhancements critical for Time Capsule to operate and recover from various conditions. Apple has fully documented what is necessary. Also, the AFP spec was expanded specifically for Time Capsule and until Netatalk 2.0.5 (linux version of AFP) was released about a month ago, it did NOT comply.
To get a DNS323 to fully function as a Time Capsule you need fun-plug, ssh, optware, netatalk 2.0.5, avahi along with new and modified config files on the DNS323. The lengthy process is totally unforgiving of typos. Also, if you plan on using it wirelessly, you should plan on moving to the 5GHZ 802.11n standard to avoid issues surrounding the overcrowded 2.4Ghz g/n world (I have my DNS323 connected via GigE to a GigE switch that is in turn attached to my Airport Extreme and I get real world performance in the range of 5-20MB per second to/from the DNS323 depending on what else is using bandwidth).
After running down the various installation processes scattered all over the web, I documented the process for my own consumption (ie at a later date if necessary). It does assume a basic proficiency in *nix commands. If you are interested in a copy of the process, pm me.
david