1. Capacitance value should be measured at room temperature and charged to 400 ± 10 VDC. The service limit of the capacitor is .315 to .385 microfarad.
2. Test the insulation resistance of the capacitor using a megohmmeter. The resistance measured between the capacitor stud and shell should be 10 Megohms minimum at 135 ± 5 VDC.[/i][/color]
Technically this is probably right, but no one would check an electrolytic by charging to full voltage.
Make sure it is discharged and measure the capacitance if you have a capacitance range on your multimeter or a LCR meter.
If you don't, no problem. Get a 9V battery and a 10K resistor and measure the amount of time to charge the capacitor to 6V. 400uF equals about 4 seconds. If it is about 3 seconds or lower, get a new capacitor. You do not need much accuracy in measuring electrolytic caps.
You can probably use the multimeter to check the leakage resistance. start with the shell and stud shorted, remove the short and let the meter rise. If it rises over 10MOhms, it is probably OK.
If you have to replace the capacitor, the replacement will probably be a different construction and much smaller. Once you find a way to mount the replacement, you will probably never have to worry about shell to stud leakage again. If you do need to replace, you will probably be getting a 470uF/400VW cap.