Why go with 4.0uF when you can get the exact 3.9uF value you need easily from Digikey for only $3 plus shipping? This is mentioned on my analog board parts list spreadsheet here:
http://spreadsheets.google.com/ccc?key=0AnmQLg8d1xThcE96S1Z0S3oxOUFiMkJEYy1nNzNuZEE&hl=en
The 250v-rated Panasonic P/N:ECWF2395JB, Metallized Polypropylene replacement cap (with +/- 5% tolerance) I recommend in my spreadsheet will last about as long as the circuit board will. It is not electrolytic, so there is no worry of fluid leaks 15 years down the line. This is the single best replacement cap you can find for C1.
http://spreadsheets.google.com/ccc?key=0AnmQLg8d1xThcE96S1Z0S3oxOUFiMkJEYy1nNzNuZEE&hl=en
The 250v-rated Panasonic P/N:ECWF2395JB, Metallized Polypropylene replacement cap (with +/- 5% tolerance) I recommend in my spreadsheet will last about as long as the circuit board will. It is not electrolytic, so there is no worry of fluid leaks 15 years down the line. This is the single best replacement cap you can find for C1.