For the 3.5mm input, look here.
You don't need a switched jack.
You can use a DPDT switch or just make sure
no to have both inputs connected at the same time...
One more thing: I cannot find anywhere a complete BOM for the 12au7 version of the SSMH. Every link points to the 19J6 BOM (http://www.diyforums.org/SSMH/bom/SSMH.htm). Surely there's a complete 12au7 version for the BOM..?
This is DIY. A little effort is expected on your part.
(found under the "Variations" menu selection on the SSMH website).
A separate BOM would be a bit of overkill to simply list new values for R2 and R8.