If you are going to DIY it then the main area that needs to be right, to avoid any leaks is the basin wastes main sealing washer, that sits under the basin between the large nut of the waste and the bottom section of the actual basin.
Best thing I could recommend that you get that'll minimise the chance of that being the area for leaks, is what's called a basin mate or seal - one of either of these >
https://www.toolstation.com/basin-mate/p37534 or this -
https://www.screwfix.com/p/thomas-dudley-ltd-basin-waste-seal-kit-3-piece-set/8795r
Silicone shouldn't then be needed, just need to ensure the basin nut is tightened up enough - try to obtain a basin waste that has a brass nut as it's less likely to strip or snap when tightening up.
You will also need to take the pop up lever mechanism off from underneath and take rod out from behind the tap and just use a click clack or my preference a captive/swivel waste.
Also, take note of the distance/dimensions of the basin trap from the waste pipe and basin as the new one will be different, it may be an idea to get an adjustable height basin trap as that'll allow some flexibility