Steam cleaning is a good way to start, although best to use main dealers coz, ya dont want sum geezer soaking the leky stuff n dist gear!
I did it to my 8v and it looks ace, cost ?25 at my local vw dealer, and took bout 25mins max. Gunk alone will cost near on ?10, so do a bit of both id say. It will make the engine finish last longer in time to come, and prevents rust as much as anything, not to mention a luvly looking bit of engine!!