For Mac you can use Heimdall instead of Odin. You can get the OSX install package
here. An explanation of how to actually flash with Heimdall in place of Odin is in step 4
here.
Basic steps:
(1) Install Heimdall.
(2) Download an all-in-one Odin package, either rooted stock deodexed EB01 or the latest Super Clean (2.9.2). Do *not* get a no-data-wipe version, since you'll want to wipe between Eclair and Froyo.
(3) Back up any data he wants to save (non-Google contacts, etc.). Note that it's hard to back up app data without rooting...
(4) Use Heimdall to flash the Odin package (according to the advice in the link's step 4), which includes Froyo kernel, ROM, and modem and a custom recovery (Red/Voodoo Clockwork).
(5) Use Red Clockwork to flash anything else you want to add/change right off the SD card -- no more computer needed.
More detailed suggestions will be in the all-in-one Odin threads, but I wanted to note how Heimdall fit in.
