panchos, your right. Quarter inch to the fitting and then 3/16 each way to front and back.
By cleaning I simply wash out the fitting hole's and brush up the brass on the wire grinder. Clean/blow it out good making sure the threads are good and clean. Don't use anything with silicone in it around the brakes.
DOT 3 brake fluid is good. I think my current bottle has DOT 4/5 on it and is synthetic. Do not use silicone fluid and don't ever let it contaminate what you have....or if you go silicone don't get it mixed with the regular stuff.
Most brake lines, if you buy them local, will have a paper tag on them stating they are either Standard, or Metric. To be sure what you were sent I would just try the brass block on the ends first to verify the sizes match...... a nice "thread guage" is handy to have around the shop to tell you what the size/threads are on stuff.
Just My opinions....
