Pretty easy job swapping a B series in an EG/EK chassis. The hardest part is getting hold of a clean engine with a matching transmission. For EK (considering you already have engine/gear), you need 2 new mounts, some additional wiring, a new clutch cylinder and new axles. You can use your original wiring with some modifications, and a P08 ecu (or almost any JDM/USDM vtec ecu) that you will have to get chipped. You might need to adjust your shifter rods too.
With K series in an EK, you will need to alter almost everything ahead of the firewall. Considering the cost of the K engine and parts, this is an expensive route.