Greetings!

I have a 2004 Toyota Highlander AWD 6 CYL - currently just over 160k miles, automatic

We started having some issues a few months ago with our headlights randomly flickering, noticed it one night while driving and it does it randomly, sometimes not at all, sometimes quite a bit, but usually stops after a few minutes. We immediately assumed it was something to do with the alternator, so we took the car to O'Reilly Auto Parts and they used their tester to check the alternator, the starter, and the battery, all three came back without any issues, so they told us to double check the connections where the lights insert, we did, and of course that did nothing to solve the issue.

Fast forward a month, and we started having issues with the dash lights (the speedometer, RPMs, gas indicator etc) randomly shut off completely for a minute or two, then randomly turn back on, when they turn back on the VSC and Check Engine lights come on. Also, the heater and ac, when turned all the way up, will sound like it is having issues with power going up and down almost like a fluctuating current or something... and also, both of our high beam head light bulbs stopped working at the same time, we have since replaced and they are still currently working, just thought it was strange that they both blew out simultaneously.

Naturally we took it back in, this time to VIP, they checked the engine codes and said that all 4 of our speed sensors need to be replaced, they quoted just shy of $700 for the four speed sensors, and then an additional $200 in labor to replace them.

Here's my issue with proceeding, my concern is that there is some deeper electrical problem occurring here, it just seems very strange that both high beam lights burnt out at the same exact time, and all four speed sensors stopped working as well, if it was just one or two, maybe, but all 4? Seems very strange to me, and since I am a low income single mother of 3, I am deeply concerned that if I spend over $900 replacing the speed sensors, that maybe they will just get fried/die again which I definitely cannot afford....

Given all of these symptoms, and the info I have provided, what is your best guess as to what is going on? I'm fine spending the $900+ if it will fix the issue, I'm just worried it will simply occur once again shortly after replacing because there is clearly some electrical issue happening here and they don't seem to want to acknowledge it or address the issue. I'm not trying to disrespect or question anybody from VIP, that is not my intention whatsoever, just looking for some other opinions on what might be the issue here?

I already have to have a tie rod replaced, get a new set of tires, and have the emergency brake repaired, so I already have a pretty big bill racking up here, so just want to be sure that this will be worth it, since the car only has just over 160k miles, I'd hate to let it go and try to get something else, particularly due to the insane used car market up here in Maine right now. Sorry for the long winded inquiry, any help or insight would be greatly appreciated!