Telling the following from my own knowledge and experience, as I since 10 year have soldering certificate for industrial/military use: First, if you´re meticulous, you should be aware if the original pcb are soldered with RoHS -solder (Restriction of Hazardous Substances - in shortly; unleaded solder). Most consumer equipment made after 2010 - 2012 are RoHS certified, and this a bit more tricky to solder - especially to unsolder. You should not mix RoHS solder with leaded solder, even that nothing serious bad thing will happens. Just have in mind RoHS solder will need more and longer heat from the solder iron.
When you want to unsolder a component for replacement, you should have a good solder iron (if you do not own an unsolder blower - but not many people do), a big unsolder vacuum pump, unsolder wick and a tweezer. Those tools are not very expensive, and well worth the investments if you´re a serious modder!
When you then want to solder, just hold the solder iron to both the component pin and the metall ring surrounding the VIA-hole around the pin - then apply the solder to the metal ring and the component pin and never only to the soldering iron, as that will generate a cold soldering and will more than likely loose it´s connection after a few year. You should apply just so much solder so the ring will be filled with solder - if you use too much so you will not see the component pin, you can remove it with the vacuum pump or wolder wick and then start over with that soldering. Just hold the solder iron enough time to letting the solder melting and it will fload out nice. If holder solder iron too long, the solder will start to bubble and that´s not good as oxygen will get inside the solder and icreasing the risk for future corrosion/oxidation inside the solder. Also remember to not pushing the solder iron with too much force and not rub it against the metal ring (this is also true when using unsolder wick) - all those three things will also increase the risk for pcb damage.
If you however had minchance/bad luck, so the metal ring inside the pcb will release but still hanging in the conductor, you may still gonna put it down gently in it´s place and resolder the component to it - if you´re meticulous, you can then paint it with some pcb paint, so no air (oxygen) will reach the bare metal. If your really unlucky, so the pcb conductor will release from the metal ring around teh VIA-hole, but you may not have to give up yet - there´s still a change you can save it by solder some thin copper wire either to the conductor by rubbing of the paint where it´s undamaged, or you can solder the wire directly to another solder joint (you can use a DVM, Digital Volt Meter set to Ohm to measure resistance to be sure to choose a correct solder joint).
If you´re not so experienced, you can apply some flux, both to unsolder and solder - as this will make the solder flow easier and fill the surface. As I told earlier in this post, you should not apply the solder directly to the solder iron - this will vaporize the flux inside the solder (exemption is just a small amount firstly, so you will get more heat connection).
Also remember; Many unexperienced people think more solder to the solder joing will be better, but this is not true - a good solder joint should be concave when looking from the side, not as a round ball. There´s also three classification degrees for solder, where the highest requirement is for military and medical use, and the lowest requirement is for consumer equipment.
Here´s a link with more information:
https://www.rctech.net/forum/radio-electronics/336870-how-solder-correctly-not-so-brief-lesson.html