hate to chime in...
If you have a DA / or QS logic board failure, then your options are limited ... Ebay usually has one or two for sale between $100-$200... most likely closer to $200 with shipping.
An Apple Retail board / Repair is out of the question of course.
I would be tempted to think hard about parting out the system and going with a fresh Intel Mini, but thats opinion only... and it depends what Software you currently have and what you intend to use the system for in the future.
If you take your $200 (most likely for the logic board), the value of the Giga upgrade on the used market (~$200?) you are already near 70% of a brand new machine with warranty, Tiger and iLife 06.
MacBook Pro Uni 2.4GHz with express card slot
iMac G5