In case of scrambled calibration constants only (due to dead battery for example) the calibration will not be that long.
All you have to do is basically 2 or 3 sections out of calibration routines, I believe CAL-01, 02 are a must Maybe 03 or more, don't remember exactly, but it is easy to figure it out as you go along.
Of all these only CAL-01 (horizontal) is rather involved and requires rather exotic pulse gen. capable of 2ns pulses, tek TG501 is the one that tektronix requires in the manual.
They call it a marker generator and I really suggest you get a hold of one.
The second thing you'll need is a "Calibration generator" , again tek calls for PG506,
but this time is not strictly necessary.
Even though I do have one and used it to calibrate 2465A, I repeated the calibration using modified FY6600 and it went fine.
Even doing it for the first time it didn't take me more that 2hr total, with practice it should take much less time.
Couple of pointers, make sure that you're following the CAL procedure for the correct serial number of your scope ! (cal. procedures for later serials are at the very end of the manual).
You will need another scope for the procedure, will be easier if that scope bandwith was >100MHz (I've done it with 1054Z, but at the fastest sweeps in CAL-01 it was sort of a guesswork
), also you will need a 50
inline terminator if your second scope doesn't have 50
inputs.
A couple of BNC cables and you god to go.
And don't be scared it is fun (you will learn how to count to 28
).