Hey UG, I have to change the tubes in my Fender HRD. I bought the amp used and it came with Tungsol 5881s (Link) and I really want to put in TAD 6L6GC-STRs Link . With this change of tubes, would I have to do anything other than bias my amp after putting the new tubes in (such as draining caps, swapping resistors, etc)? Because if not, then I'm going to bias it myself and save some money. If I have to do anything more, then I'll just bring it into the shop.
Also, any good preamp tube recommendations?
"The most important thing about music is energy and emotion, not how well you can play. Technique should be a tool to achieve your vision, not the other way around."
-Jeff Tuttle

More guitar, less ultimate-guitar!
5881's are generally more durable versions of 6L6's. You can even get away without rebiasing, but its a good thing to do after time anyway.
You COULD replace the screen resistors, but unless you are experiencing issues (with performance and/or sound) you don't need to. The HRD isn't that old yet, so the components generally haven't worn out yet, so there shouldn't be anything to replace, unless of course it is broken.

Have fun with the amp, HRD's are sweet, I absolutely love mine. I went with JJ Tubes, the rebiasing is very simple. I use 6V6's though, I prefer the breakup at a bit lower volumes for jamming. For preamp tubes, I prefer JJ ECC83S in V1, ECC832 in V2 (It helps bring down the gain and make the OD more natural sounding) and a Balances ECC83S in V3.