Q: ibook G4 issues

If you have the install disc set for Tiger 10.4.x that accompanied the computer (or whatever it has inside, now) you could see if the computer could be started up from that disc, hold C key on start with disc in the optical drive; and try and fix the issue. You can use Disk Utility without running the full installer setup from the menu inside the booted install disc. And you can't use an install disc from another model/series/build year to upgrade a system in a different computer. Hopefully your 10.5.x install disc is a retail full install version.

Before upgrading a failed computer, you should see about troubleshooting the actual cause then fix it, first.

Could be the system is not correctly chosen in the installed system or has some defects, or perhaps the original hard disk drive has failed; and other possibilities arise as the vintage gets only older with time.

The RAM upgrade is not too hard and iFixit page has information on how to get into that area (under keyboard) to replace the RAM chip with a larger capacity one. It can use a 200-pin SO-DIMM PC2700 low-profile/low-heat 1024MB chip of quality manufacture. The cost of these has gone down from when they were the newest thing. Be sure it is not a poor brand, a known good high quality brand chip could even be previously-owned if the series, model and type of chip is the exact one for the computer you have. However I had found used ones were more costly than new, by mail-order, & new are guaranted.

Anyway, hopefully this helps somewhat.

Good luck & happy computing!