I highly recommend PEX Tubing and SeaTech push fittings. All you need to know is what diameter your existing copper is.
At the regulator yours will be 1/2 in. The fittings should be about $4ea and 5ft of PEX will be less than $5. Pickup a compact tubing cutter and get rid of any copper that is leaking and be done with it. If you replace anything wih flexible braided tubing you will always and forever have small dribbles no matter how tight you get them from seasonal heating/cooling expansion/contractions ****UNLESS**** you put a barbed fitting on the copper.. I know-I've tried.
Lowe's Home improvement, and RV Dealer that handles Coast, or www.dtiparts.com
are good sources for the PEX SeaTech Combo.
Here are some pics. Not counting the reomoval of the copper. All of the pictured work only took about 30 minutes.