M-HZ

I could use a bit of advice regarding a 333A which a local resident has offered to sell me at a fairly reasonable price which is still under negotiations. It is in rather good shape although the Frequency Range rotary switch may need a cleaning as would the Meter Range Set level. I gather a high quality cleaner would do the trick? The 333A is functional, rail voltages are fine,but has not been calibrated for some time. I do not have access at the moment (specialized instruments) to produce 100uV, 400Hz sinewave signal nor any other high level calibration instruments, but may have acess in the near future. Having done a complete overhaul (J) which looks phenomenal and working as new would anyone have any suggestions for an immediate attempt to bring this unit, if purchased, up to some form of of reasonable performance? I will mainly be utilizing it for measuring THD+N in tube amps/guitar and other forms of experimentation along these lines. Thank you!