This is a two part question really.
I have done a lot of googling to see what chips are common these days. There used to be various Motorola PLLs but all seem to have been discontinued. The popular one seems to be the ADF4116.
DDS is a neat way but you get massive harmonics and then need to spend loads of money on filters...
On the attenuator, I've been looking at how signal generators do it, and they all seem to use really antique methods involving switching in and out various size steps e.g. 1db 2db 4db etc.
This requires complicated software sequencing (especially if they use reed relays) to avoid massive output spikes. Some use MOSFETs or even PIN diodes but diodes need fancy circuitry to bias them forwards to get the correct "resistance".
Maybe that is the only way to do it if you are going to to GHz frequencies, but for say 200MHz can't one just use a multiplying DAC?