Due to unfortunate circumstances I have acquired a lot of vintage amps. I am good with solder and understand how things work electronically. Have watched webers video and read a book or two on tube amps as well as worked on a few when i can get direct replacements. MY skill is terribly lacking however in finding good "substitutes" for caps when I can't read or match up a vintage cap directly. AND if I should use mica/mylar/polypro etc...as well as the voltage requirements for caps/resistors. Would like to keep things relatively correct of course. No problem with tube substitutions...seems there is plenty online for that. ANY??? Books/advice other than the proverbial "experience...don't know how bad I wish I had that!" on what is a good substitute for what (what values come near enough and what the difference in bass/treble/distort/heat etc... would be?) ... always go higher?? I know this is a mouthful and a huge hill to climb all at once, but when I get ready to order via mouser I just 2nd guess and 3rd guess then tuck my tail between my legs and wait.... I haven't seemed to find any literature on replacing vintage parts with equal enough values and so forth. Really appreciate all and any wisdom imparted.