2010 Toyota Corolla 140,000 miles manual base model brought to the shop for the first time just to find out the brake line is corroded/rusty in multiple areas including the front near master cylinder and on the backends near the rear tires and on the connectors to the wheel itself. Dealer wants to charge absurd money to fix, is this something I should replace myself? Brakes are critical to safety and I've never had to work on this before. Or should I leave it to a professional and bite the bullet for labor costs? My knowledge extends to brake/rotor/caliper replacement.
Dealer wants to charge absurd money to fix,
Don't go to a dealer, that's always the most expensive option. Find a good independent mechanic (not a chain shop).
is this something I should replace myself?
Do you know how to double-flare brake lines? If you have a good flaring tool it's not too difficult, especially if you replace the rusted steel lines with NiCopp brake line which is very easy to bend and flare. If leaving part of the old brake lines in place you would need to cut and flare the old steel line where it's still good and use a union to connect it to the new line. (I usually replace the entire brake line.) You can also buy lengths of brake line already flared and with fittings.
Then there's the issue of bleeding the ABS-equipped brake system. You'd likely need a bidirectional scan tool, especially if replacing lines going to the master cylinder since air would wind up in the ABS controller.
However if you're not comfortable with the idea of doing it yourself it would be best to have a mechanic do the work.
YouTube video out there it doesn't seem difficult as long as I can get my hands on a flare tool and cutter.
You'll want to practice on some scrap line. As I said, NiCopp is much easier to work with than steel.
You don't have to spend a fortune but don't buy the cheapest flaring tool out there either, it will just make your life miserable. I recommend the kind with individual dies for working under the car in tight spots. I have this set, ATD 5483 and have done several brake line jobs with it:
It comes with multiple sized dies so you can also work with rusted fuel lines, etc.
Eastwood sells a 3/16 flaring tool (that's the most common size for brake lines) that has good reviews but I have not tried it myself:
https://www.eastwood.com/eastwood-on-car-flaring-tool-for-3-16-tubing.html
Be sure to put fittings on the tubing before crimping! I've made that mistake too many times!
Do you know how to double-flare brake lines?
Never had to before. I've watched just about every YouTube video out there it doesn't seem difficult as long as I can get my hands on a flare tool and cutter. I'm willing to put in the work, I was looking to get the pre-cut fittings figured it'd be better than trying to do everything from scratch myself. I'll have to see what an independent mechanic would quote me.