The title of the thread "Architectural Retouching" - actually covers different areas. Its a very large field and there are many people earning very good livings doing this alone. Some knowledge of 3D is becoming more needed in this area, but KittyBuddha if its an interest of yours there is a living to be made.
As Ant has again correctly pointed out the samples on
here are not that great, they are more interiors than Architectural retouching. In fact IMHO most of the befores look better than the afters. They are oversharpened and oversaturated. It doesn't help that the jpegs on his website are massively overcompressed. But even though crude gradated dodge and burn, and overuse of local contrast has turned these reasonable starting shots into what honestly look like 3D renderings (more Max than Maya). Thats just my opinion.
Most professional architectural retouching works in conjunction with 3D sotware such as Rhino. The software can generate wireframes or or alpha channels as well as 3d renderings. The retoucher then uses the images provided to him and then "pimps it up" in Photoshop in a way that makes the architects client go "oh yeah - Ill buy that £300 million worth of glass and sandstone".