wolfiegrrl:
1. Salvaging your old HDD is a good idea. Removing the HDD from the computer is quite an intensive job, but quite doable if you can manage a screwdriver and be focused. You will find directions at
ifixit. If you decide to go that route please post back for some tips.
2. If you salvage your old HDD you can place it in an external FW enclosure and use it as an external HDD.
3. I do not think repairing/replacing the logic board is financially advisable. The money you put into it can go toward a new computer. You may sell the old iBook for parts, as there may be parts that are salvagable and useful to others. e.g. the HDD ribbon cable, the monitor itself, RAM etc.
4. The Aluminum PowerBook G4s are very good computers. They are not as powerful as the Intel Macs, but they are plenty powerful enough for most ordinary users. If I were to replace my old Pismo, that is most likely what I would choose for myself. Another argument in favor of the PB G4 (or any PPC computer) is that everything you now have on your iBook G4 by way of applications, will be instantly compatible. With Intel Macs some things may be different.
Obviously you will want to be careful about what you buy. Be aware, too, that one can easily get a brand new computer that comes with issues, as an older one. One of my daughters has the 12" PB G4 1.5 GHz and loves it dearly; one of my grandsons has the 15" PB G4 1.67 GHz and loves it. Both of these computers were bought on eBay, too! If you are interested in pursuing this further and need some pointers, I will be glad to share some information.
Good luck 🙂
cornelius