You have not given us a more detailed description of your issue. Is it worn bearings that require replacement of the cooler unit, or is is a control issue of simply changing speeds and sound?
IF you decide the cooler needs replacement, I see now that there is no simple way to replace the FAN only on that cooler unit. You must replace the whole thing. This video
View: https://www.youtube.com/watch?v=FwpHbNS4suQ
shows how to remove that cooler and clean off the old thermal paste. In cleaning off old paste, do NOT scrape or scratch it! Sometimes a clean tissue or rag with a modest amount of rubbing alcohol on it can help to soften and remove old paste. NOT a LOT of alcohol - don't want it to drip down under the CPU. Make SURE the CPU surface is clean and all DRY before proceeding. It goes on to how to re-install the same cooler. IF you buy a different replacement model, follow the install instructions for that new unit.
A few hints.
1. For REMOVAL, sometimes the thermal paste is old and dried, and the cooler does not want to lift off the CPU. DO leave the CPU chip fastened in its socket for this. AFTER undoing the four hold-down "screws" you may want to try "rocking" the cooler and / or twisting it gently to try to break the seal so the cooler can be lifted.
2. If this does NOT work, another technique is to ensure everything is back as normal with the case open, and start your system up. Let it warm up fully and this may soften the paste. Now shut down and disconnect from power. Again, ensure the hold-down "screws" have been undone, then try again to move the cooler around and loosen it with the softer paste.
3. NEW thermal paste must be used as you install the new cooler. It may come with some, or you might need to buy your own. HOW MUCH to apply is important - too much is just as bad as too little. Follow instructions for YOUR CPU chip. An example is shown in that video. A good technique is to apply the "blob" in the middle, lower the cooler onto the top of the CPU chip already fixed in its socket, then twist it a bit in both directions with little pressure to spread the paste. Finally align it in final position and start screwing down the fasteners. Follow the instructions with the cooler. Many advise PARTIAL tightening of screws on opposite corners, then further tightening in stages to ensure even pressure all around.
4. Depending on what the new cooler is, you MAY not be able to make all its connections and mounting screws work unless you remove the entire mobo from the case so it can be properly supported on a clean dry surface for work.