Help on possible head rebuild

Hello everyone,

I am pretty new to owning a TDI and have been doing my best to fix her up. recently I have had a growing concern about my cars ideal and slowly falling performance. There is a slight hiss coming out of my exhausts. my blow by is by no means bad but I am starting to thing I might have a burned exhaust valve or possible hydraulic lifter fail. Now my engine is a CBEA and if anything, I would do the timing, serpentine belt, and tensioners while I'm in there. I'm wondering if it could be anything else that I wouldn't be thinking of but if anything, I would want to know what would be more cost efficient to get the head rebuilt or do a swap.