Concur, simplest way is to replace fan.
Baring that, Yes they can be replaced. Not knowing your experience/knowledge - They are polarity sensitive so need to observe +/-. No damage if reversed, they just do not light up. Exception - ones used in an AC circuit which will light on one alternation and off the other alternation, NOT normally the case so will not go into constraints
Repacement LED come in several flavours, most are approv 2 volts and draw 20 mills (supper bright about 30 mills). There are also one that operate at 5, 6, & 12 V so need to get the correct voltage. Ones above 2 volts use a series resistor either internal or external to the LED. Example a 12 V led wil have a series resistor of approx 600 ohms.
Can you post a link to the fans so that I can get an idea of placement.
Should not be difficault.
Is it possible to just pull the led away from the fan housing. If so there should be only two wires to the LED. Cut these two wires and locate so that they can not short to one another. maybe a small piece of electrical tape or superglue. Repeat for other 3. It is possible that they are connected in series so that disabling one disables all 4. To find out after you "cutout" the first one reconnect to power to see if other three still lite.
Safe, Just cut the Two wires and safe so that the ends do not come in contact with one another.
There not connected in series, and yes i have room to pop them out so i can cut the 2 wires and glue it so it will not inter connect. Sounds like a plan lol. There spacefans lol i cant even find a link.
If you grip the fan wires about 1cm from the fan body (not at led end, at the point where/near it is soldered onto the pcb) and rotate it,
you should find that it comes off at the solder point, no need to cover/glue anything then and no risk of any shorting in future.