Relay r12 (brown) located on flip-down interior fuse panel is easy to replace, it just pulls (wiggle or use yellow fuse puller} out of socket. Should be no more than $20 but I'm just guessing. However, I'm not able to say for certain that this relay is the cause of problem. Pulling relay out will cause lights to go off, which maybe a better situation for you pending fix.
In these situations I can simply substitute from my other car to confirm problem solution. You only have the option of substituting a similar relay from the under hood fuse box by the battery. The horn relay r7 is similar type (brown, closest to battery) and you may wish to substitute it inside the car to see if that fixes problem.
These relays are indentified in owners guide BTW, if you don't have one try this:
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=general&Number=61629&page=5&view=collapsed&sb=5&o=31&fpart=1
Should have my EVTM tomorrow, will have a further look then.
