There's a little button that looks like a picture. Click it and then you can add a pic from your computer. When the following window comes up click "Add media" Then in the next window you can drag the image file into the window, or click "or Browse for files"
It sounds like the door open sensor may be damaged. There are ways of tricking these sensors so that the device thinks the door is always closed. You can see the door sensor in this guide, it's at the top right of the green PCB, in step 6, just above the two green wires and white connector. Sega Dreamcast GD-ROM Replacement
It is unlikely that your battery will suffer a catastrophic failure just because it's old and doesn't hold a lot of charge. I've had laptops that could only power the laptop for five minutes or less before shutting down because the battery was so weak. They worked for a long time with no problems, other than battery life.
It's okay, you're a Mac User. ;-p Sorry, I couldn't help it. Okay with that silliness out of the way, you will want to get one of these. https://www.amazon.com/Sabrent-5-25-INCH-Converter-Activity-USB-DSC9/dp/B00DQJME7Y/ref=sr_1_17?ie=UTF8&q...-17&keywords=usb+hdd+adapter This way you can remove, or have someone help you remove the old hard drive and connect it to the computer via USB. If you have any nerdy friends they probably have one already.
Husqvarna makes this mower for Sears. It's powered by a Briggs and Stratton engine. The link below takes you to the Sears Parts Direct page for your mower. https://www.searspartsdirect.com/model-number/917287380/0247/1509200.html There are probably better places to get parts but that should get you started.
The orange strip you mention is the display cable. It's just like the cable that connects a desktop to a monitor, only much smaller. On mobile devices these ribbon cables can be a real PITA to reconnect. It's possible that when you reconnected the cable it didn't fully re-seat. It may have looked fine but all those little copper pins may not be contacting properly in the socket. I would recommend opening it back up and attempt to re-seat that cable again. I would pull it out and reconnect it. Many of those ribbon cables have retention mechanisms, so make sure you got it. Also be careful, little ribbon cables can be very delicate. You may want to get some additional help if you don't feel comfortable doing it. Good luck.
Unfortunately a MacBook Air, doesn't have an ethernet port, so she would have to get a USB -> Ethernet adapter to try that. So I found a You Tube video that deals with this issue. I watched it and it seems like a legit video. But don't have a MacBook on me right now to test it. If you are still having issues I can get a MacBook tomorrow and try it . https://www.youtube.com/watch?v=FydtdMJ4... What he suggests in the video seems plausible since the config files that are modified do control many aspects of the wifi network card performance. Good Luck
LCD panels like to run at their native resolution, they usually look like crap if you run them at different resolutions. I would recommend running the laptop at 1920x1080. If the fonts are very small you should bump up the DPI. Assuming Windows 10 Right click on an empty space on the desktop. Click on "Display Settings" In the main window that pops up there is a slider bar labeled. "Change the size of text, apps, and other items: 100% (Recommended)" It may have a different number, but it will probably be 100%. Try adjusting the slider to 125% or 150% and see if that works better for you. You will need to log out and back in after making this change as not everything will change until you re-log. Good luck.