The hardest part is getting the nuts loose. Use "flare nut" wrenches.
The slot slips over the line and gets a firm purchase on the nut.
I believe these may be metric. Someone will correct me if they are not.

Loosening the nuts from the caliper themselves is the critical procedure. If those come out, you are okay. The calipers may have other problems, but at least they will accept new lines. Do your brakes work okay now? The steel lines can be replaced fairly inexpensively. The rubber ones cost quite a bit.

There are also slide on clips at the joint of rubber to steel which hold the line in the mount.

Spray everything with PBlaster (sutoparts stores) a few times for a couple of days prior to starting, it may penetrate the joints and make removal easier.

Brushing the loose dirt from everything will lengthen the life of the brake system. Dirt is it's worst enemy.

If you are removing both the rubber and steel lines, you can cut them to make getting at them easier. Save the steel parts, line them up and measure the length. Ready made steel lines are widely available at auto parts stores. Ask at the parts counter.

The rubber lines are make/model specific, and they have to be the right length so that steering and suspension movement is accomodated.

After the parts have been replaced, air will be inside the lines. They have to be "bled", by opening the bleeder nuts on the calipers and pressing the brake pedal to force fluid through and the air out. It makes sense to buy a cheap brake bleeding kit, otherwise you need a 2nd pair of hands (or rather, an extra body with a foot). Instructions come with it.

You can save hundres of dollars doing it yourself.

Oh, and buy a Haynes manual. Cheap and many on ebay.

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MPergiel, Elmhurst, IL '74 145e T-5 'Orange Alert'