DIY is not too difficult. Just taking care to clean and keep track of everything. I did mine last summer and the result was marked improvement. Depends a lot on the shafts.
I replaced the teflon bushings on the shaft ends and it helped quite a bit, but still had some leakage at other journals so I decided to re-shaft them.
Re-shafting is the point of no return of a rebuild though. It requires a special piloted reamer and preferably a lathe. Here's a great video on the process: (it's for an SU carb, but the process is the same for a weber):
https://www.youtube.com/watch?v=Yeu-t9ojtBc&t=531s
Good luck and lots of helpful people here either way you go.
Karl