If it were me, swap it. I am basing this purely on my love for the Mk4 R32, common sense out the window. Truly believe (aesthetically) it looks much better than the Mk5 flagship models. Would love one in the garage as a project.
If you know it's history and can get it all checked out and all (very overdue) the maintenance sorted out, why not.
Couple on PistonHeads and 2 stunners in Black on Autotrader, all around £6k ish. Go for it, they sound bloody gorgeous.
Note to self: stop looking at Mk4 R's