Is swapping a 4.8 LS harder than a 5.3, and how hard is the wiring?

No harder — it's the same swap. The 4.8 shares the 5.3's block design (six-bolt mains, 3.780 in bore), cylinder heads, intake and PCM. The differences are inside: a shorter stroke (3.267 vs 3.622 in), different rods and a different cam. Speedway says most of what's made for the 5.3 works on the 4.8, both for swapping and for power.

The wiring is the same job as a 5.3 of the same generation: an LR4 (1999–2006) is Gen III, while the LY2 (2007–2009) and L20 (2010–2014) are Gen IV, which changes the crank reluctor and the computer you need: 24x (Gen III: LS1, LS6, LQ4, LQ9, Vortec trucks through 2006) uses a 1x cam sensor; 58x (Gen IV: LS3, LS7, L76, L92, 2007+ Vortec trucks, 2007+ LS2) uses a 4x cam sensor. Exception: 2005–06 LS2s are 24x, so they need a 24x harness and computer. PCM, harness and sensors must match; a Gen III PCM on a 58x engine needs a conversion box. Match the harness and computer to the generation — see harness, computer and tune.

4.8s were never built with AFM, so there are no AFM lifters to worry about.