[Elecraft] K3 upgrade to K3S question

[gt-i at gmx.net]

Hello list,

I've purchased a used K3 S/N in the 3ks, and plan to apply some of the 
K3S upgrade options.
Any experiences, hints or do's and don'ts to tell for me?
I'm using the K3 mainly for HF contesting, VHF with an external 
transverter and some DX chasing.
tu es 73
Gernot, DF5RF