This will be extremely difficult to solve on-line as you have limited knowledge of HW. Most solutions here are for folks who have manipulated HW to a fair extent and can figure out things with a suggestion which is all that can be done on a forum.
For example, the keyboard/mouse and the ram and most probably the cpu are ok but they have to be tested on "known good components". If there is none, then a pc repair shop, where they do have these, must be used. That is if you consider the hardware worth saving. If the motherboard is gone, most folk with things over 2 years old usually go for a new system, such is how technology is evolving nowadays.
Also with no reference to what you have as hardware, it is decidedly hard to help you. If you are like me who got tired of repair shops ripping me off (charging really, it is hard to prove they are really ripping you off), then it is time to start taking apart things like your husband apparently has. If you find computers indispensable, then it is a must.
Of course it is just my opinion but having the HW physically, I can trouble-shoot most anything but that is almost 20 years of experience. The thing is that I made the decision back then and have not regretted it to-date, hehe. Sorry to not be able to be of more assistance.