Unless designed by the same manufacturer, soldering iron tips aren't typically interchangeable. However the procedure of removing and swapping the iron's tip is generally the same.

What size solder tip should I use?

You should opt for a chisel tip, which are perfect for wire, desoldering, through-hole, and surface-mount soldering. Ensure the tip is sixty percent the width of the soldering pad, so that you minimize thermal stress to the component while speeding up the process.

What is the difference in soldering tips?

The difference between these two is that the D series with its chisel-shaped head has a larger surface area so more heat is able to be transferred, arguably making most soldering applications easier. For more detailed work, you can use the needle-point I series tip.