New caps for preamp?

Yes. 1.Caps are better now,2. price constraints on manufactures lead them to use lower quality ones, 3. time to change anyway for best quality, hard to hear gradual deterioration in sound.

If it ain't broke don't fix it!!If it works and sounds fine ,spend the money on more music.

Different caps will change the sound for sure.

If its an improvement or not depends on which way it shifts the balance of the sound.

You might want to call the mfg of the preamp and see if they have any recommendations.

John C.

If the amp was always working for all these years than most likely you'll need to worry. Otherwise I would check/recap the amp especially electrolytic caps. They're most-likely dry and need to be checked with either cap tester or C-meter for the specified parameters. Each of these caps may cost around a dime(no need to shop for the 'improved ones' the originals are the ones the preamp is specked out for) at parts retailers and would extend the life of your unit by another decade or more.
That would require knowlege of testing and replacing electrolytic capacitors from the circuit board. Giving the unit to the local tech would hit your pocket much harder if you figure...