How to replace hardwired stock power cord ?

Unfortunately, there’s no, "standard" size for IEC connectors, so no one makes knockout punches, for those animals(to my knowledge, at least). Some rectangular punches are available, but- the prices typically aren’t realistic for limited usage(ie: https://www.amazon.com/Greenlee-60031-Rectangle-0-750-Inch-1-140-Inch/dp/B00204DWQI ). I’ve modded a few ARC preamps, which had aluminum chassis(easy to drill/nibble/file to shape/size, without a lot of metal flying around). No familiarity here, with Nak’s later(digital era) chassis materials(was steel, way back when). With a, "captive" cord in steel: I’ve found it easier to install upgraded cords like the following Zu examples(round/small diameter), can be installed through a rubber grommet, without any chassis alteration and soldered, internally. Of course, if you wanted a larger cord and don’t care about modifying the chassis: enlarging the original hole with a drill or knockout and using a bigger grommet’s an option. https://www.zuaudio.com/cable/mission-power-ii If you can find one of these, you’d be hard-pressed to improve on it’s performance (with a CD changer/DAC), at a reasonable price point: https://www.zuaudio.com/classic-cables/mother-power-cable

As far as your unit’s capacitors: if it were me, any electrolytics would be replaced with the exact same values, in either Elna Silmic II’s, their Cerafines or Sanyo OS-CONs. Most DACs have regulators that can be upgraded, as well, to great effect. (https://www.partsconnexion.com/capacitors-ele-elna-rfs-silmic-ii-series.html ) (https://www.partsconnexion.com/capacitors-ele-elna-roa-cerafine-series.html) (https://www.partsconnexion.com/sanyo-os-con-electrolytic-capacitors.html) (carefully observe polarity, when replacing electrolytics) (https://www.partsconnexion.com/belleson-SPX78-regulators.html

Thanks rodman99999........well I had hoped to replace it with Furutech    https://www.futureshop.co.uk/accessories/connectors/iec-power#page=1

I don't mind cutting out the rear side of the case to accommodate this - but then - is soldering just straight forward ? 

I have no experience in changing the capacitors ....wish I could. However thanks for the info....much appreciated.