About the sockets, take a look at these.
You are absolutely right so simply finding some 2SK389's is well worth it or just bending the legs of a metal can LSK389.
Yup, those are LED's and the RLED can be what ever you want it to be. It runs off the +15VDC line so a 1k5 resistor would work or something like the 3k3 which I use since I hate bright blue lights.
Yup. No need for chassis mounted heatsinks either so any box large enough will do.