I don't know if this is still relevant, or if you're even paying attention, but I'm working on an ASHX header file that will replace an old VB6 CGI program we have to convert between Lat Longs and PLSS. This crummy old VB6 program is dying (and about to take our Apache server with it), so I'm rewriting it using C-Sharp in an ASHX file. Our old system queried against a MySQL database that contained the Sections, Townships, Ranges, and all the way down to 10 acre tracts. That MySQL database is pretty out of date too, and the program doesn't always return accurate data. This new system will query against an ArcGIS server (using SOAP)
We have an issue in some of our web applications that if a user selects a 10 acre tract, we need to return a lat-long (just the centroid of the 10 acre tract) knowing full-well that's not terribly accurate, we still would like to have the center, hence the "conversion" from PLSS to lat longs.
But ultimately, if you still need something like this, if you have the service in ArcGIS server, it's not too terribly difficult to do. Just Query for the legal description you need, take that polygon and get the centroid of it (for our SOAP service, lacking a Centroid option, we're using GetLabelPoints). So really, to do this all you need is a Query.
