The condenser swap isn't too bad a job although I don't know exactly what you need to remove but I don't think you have to remove the water rad etc.
I was charged £300.00 for the job and thats remove old, fit new, and regass etc. so the labour element was probably 3 hrs all in I would say.
If the leak is on the joint it is still likely to be down to the condenser corroding. I had this on a Mitsubishi - no matter how many O rings we tried the joint still leaked, I even sent off for the original O ring from Japan and it still leaked even though the joint faces looked really clean. In the end only a new condenser sorted the problem with it's new joint.
You are bang on time for a new condenser anyway - 7 years is the max. My 1999 failed last year, at 7 years.
When it finally craps out it looks like this:
Leaves and dirt all collect in the bottom of the black plastic fan housing at the front and cause the aluminium to perish. The green stuff is the refrigerant oil pissing out. This all happened within 1 week and the a/c crapped out.
I have a lovely new condenser now and a new fan (different, expensive story) and the a/c is fantastic with air-off temps of less than 5deg C
