The main problem with trying to clean the fan is that you must take the Time Capsule apart....which will void any warranty that might be in place at the time on the product.
The Time Capsule also tends to almost self destruct unless you use extreme care when you open the case up to pull out the internal components. Ribbon cables and connectors are easily broken when you try to remove the components and boards.
It's not hard to clean the fan once you find it using compressed air, and if it has been "screeching" a tiny drop of fine machine oil will probably be needed to quiet down the bearings. If that does not work, you'll have to look for a replacement fan......(which Apple does not sell)....on the Internet by using the manufacturer name and model number.
If the Time Capsule is still in warranty and it starts overheating, or the fan starts getting noisy, if possible, it is far easier, and a lot safer, to copy the data from the Time Capsule to another drive and then have the Time Capsule replaced under warranty.