Yup, photos of the motherboard will be 100% helpful. The usual place to look is at the front in the middle - where the keyboard plugs in, between the CPU and kickstart chips. The evil battery will cause havoc. Look for corrosion from the battery outwards.
Sometimes they can be repaired or you will have to build a new motherboard.
Otherwise, remove all the cards from the machine so you just have the monitor plugged into the machine and the power supply. You should get a kickstart screen if things are working. Go from there.
We usually have a monthly meetup - so you could bring it along to that.