Not terribly hard if you have the correct tools. Basically, you drill the mounting holes, counter-bore the inside (barrel channel side) for the T-nuts, install and epoxy the T-nuts in place filling the counter-bore to even with the barrel channel with the epoxy (install the rail and bolts before doing this, and use some sort of release agent on the bolts so they can be removed later if needed) and put your barreled action back in the stock.

Fastener kit - http://www.accu-shot.com/catalog/pro...products_id=73
Rail with Flush cup in it - http://www.accu-shot.com/catalog/pro...products_id=64