east west mix

Hi everyone and apologies for my first post being a HELP ME one

I've recently acquired a 2004 Legacy 2.5auto which I like as it suits my needs perfectly.

A fault has developed however - had it up on ramps at local mechanic's today to check for brake fluid loss problem (500ml bottle used in two days)

Problem appears to be brake line which emerges from body of car just in front of rear right wheel, then splits into two with a pipe going over/above petrol tank to rear left brake. Apparently this looks an absolute nightmare to access and replace and local garage is reluctant to put a guide price on the repair, saying it could take over a day to do etc. The garage has a reputation for reasonable rates and is not considered to be a rip off merchant.

Is there an easy way to access this and replace the pipe or is it as major a job as they are suggesting?

Any help/advice appreciated