I've fixed my first unit using the FSP200-P35-A54 PSU from Digi-Key. It was about $60 shipped with taxes.
The original PSU has 8 screws securing the PCB: 4 inner and 4 outer screws. To remove the PSU, just remove the 4 outer screws and gently pull. There is a thermal pad underneath that you will want to reuse. I reused almost everything. Remove the 4 side screws holding the power components to the heatsink (you won't reuse these). Remove the 4 inner screws (you won't reuse these either). Pry a little on the sides of the components to separate the board from the heatsink. The board will come out once it's free. Save and reuse the thermal pad from the big IC that's attached to the inside of the heatsink. I placed this on the black metal thermal bar on the new PSU, making better contact with the heatsink during reinstallation.
Remove the white plastic film from the bottom and save the thermal pad inside attached to the bottom for the new PSU. The white plastic film has 4 holes for the inner screws; we no longer need these. Cover these holes with electrical tape. One of the holes is your AC lead wire, so be sure it's hole is well insulated. I had some interference issues with the new PSU and the 4 inner screw studs attached to the heat sync. Remove all 4 inner studs from the heatsink since we can't reuse them anyway. They're just pressed in and can be removed with pliers. I didn't need to grind them down or anything. I put the inner screws in backwards to give my pliers some leverage to tweak them enough to pull each of them out.
Now that your heatsink no longer has any studs, reassemble everything with the new PSU but only use the 4 outer screws. I was able to get everything back together properly/secure with just the 4 outer screws, including the top & bottom plastic covers. You absolutely DO need to swap the pins on the power cable as previously mentioned. The PSU
datasheet clearly shows which 3 wires are ground and which are +12V. The PCB board also indicates this. I used the tip of a pocketknife to get each wire out, one at a time. It takes some patience, but I prefer this to trying to swap and potentially break the connector on the new PSU. Push each pin in further into the connector, then depress the clip with a knife or tool, then pull it out. Also, since the board is clearly marked, the cable should now match the new board in case someone else comes along to look at it later on.
There's also a ground spade connector on the new PSU board. I decided to connect it to the chassis grounding screw. This is probably optional, but more grounding is better IMO. The old PSU was only putting out 48V, making a weird squealing noise, and constantly wrote the following error over and over again each second to the console:
PoE Fatal: Vmain (48V) fault has forced all ports on slot 0 to lose power.
I'm glad this switch is finally working with a new power supply. PM me if you've got questions on the PSU install.