How or where should I start in redoing my kitchen?

Greg has some good points but I would start with painting your walls the color you want. Once you have painted your cabinets, you can't go back without stripping them. Not a fun job. Painting your walls will lighten your kitchen a lot. If you can't afford a new light fixture, try Led bulbs. They give off sooooo much more light. Don't be afraid to tackle this. Each step will be an improvement.

Also add some lighting on top of and underneath your wall cabinets. Rope lighting works great is costs very little.

The first thing you have to address is the wall and ceiling. It makes no sense to make cosmetic changes and then have to pull down the wall because of rot.

Kinda funky layout. Consider removal of the crosswise cupboard/counter (dividing k and d) and building/buying an "island" for more functional workspace. Agree re needing paint to brighten and (chalk?) paint on cupboards to cut back on all similar wood. See if ReStore has some shallower cupboards if more storage an issue b4 embarking on the cupboard "paint" and a hue of whatever you select for those, would do on wanescoat (sp? sorry) on rear/window wall. Really strong horizontal lines need some breakup. example, cupboard fronts over sink go up to ceiling instead of all horiz. flush. As for lights, you'll have plenty of time to keep your eyes out for the perfect one but invest in some non blue LEDs in the interum.

STOP EVERYTHING! These suggestions are all nice BUT in my experience, any successful project starts with A LOT of research. You need a master plan, even if you aren't going to see it completed for several years. Don't use money as the guiding force. Find out what you truly love, and as you can afford each phase, complete another phase. We've been doing this for 2 years on our home and it is now nearing completion. We have been truly in love with our improvements and are now past the awkward adolescent stage where nothing matches and have moved into the beauty phase. Really, you won't regret having a master plan.... A vision....

Your Hubby is right about at least one thing. The wall where you had toilet overflow needs to be opened up. Don't put any bucks into redo until you know you have a clean slate. In the meantime start visiting home improvement stores with your current layout and measurements. The people in the cabinet department will help you find the most useful layout for free. I learned so much from them. You can even get an estimate for what you like. This way you can decide if it makes sense to just do it piecemeal. New cabinets today have it way over old in terms of space and access. Good luck with your project.