How hard is to repair rust around the rear window? You can see pictures of the rust at : Rust (http://community.webshots.com/album/69593663QSEvGO)

According to the posted pictures.. your 1/4 panel and trunk filler pannel have rust in the Window channel..
You frist remove the window.. I like to spot sand blast the chanel area to eliminate all the Rust..
Then Bend strip of metal 20ga. at a right angle.. I Then cut out the rust area with a cut off wheel..( Wizzer ) and cut A patch peice from the newly formed steel. .. The corner is the hardest,, If you have accesss to a shrinker it makes it life easer.. another way to skin that cat...is to cut slits on the one side of the 90 and bend it to fit the corner. After it is shaped to the radious use a Sharpie and mark the overlaped on the sloted side and Then cut the excess off.... It's allot of welding and finishing but it'll makes a Permanent Fix....
to this vary common problem...