Unplug the PS1 and use a small flathead screwdriver to gently lift the glass fuse from the fuse holder. If your model is SCPH-100X or SCPH-550X, the fuse size is 5mm x 20mm. The current rating should be specified next to the fuse holder, the clamping clips you've described. If anything, the fuse itself should have some markings indicating its rating. If you use an Isoclean fuse, they are directional with an arrow pointing in the current direction. The arrow should point from the rear of the chassis toward the front of the chassis. Once replaced, plug in your PS1 and enjoy.
I would recommend a good power cord before investing in fuses. The PS Audio or Furutech C7 power cords are great.
I should also mention that Jeff Day's recommendation of the Walmart Woods Yardmaster Patio cord for speaker cables is an excellent one. I paid $7.88 for 40 ft. I didn't even add connectors; I'm using bare wire ends and the cables are surprisingly musical. If you like the PS1, try the Walmart White Lightning Moonshine speaker cables.