HELP PLEASE!!!!!!!

2004 S80 2.5t auto

Hi everybody...... Hope your all good!!!!

Now..... A few weeks ago I was driving home from work and noticed that when I took my foot off the accelerator the car wanted to stop and not cruise along (Straight road no hills) when I finally arrived home and got out I was greeted with a lot of heat coming from the driver's side wheel area so I then began to see if any of the remaining wheels we're the same and yep it was the same on the rear left-hand side...... So that's the driver's side front and the passenger side rear..... So I'm thinking that the callipers have failed and need either new callipers or they need both need stripping down and rebuilding.... And also I've noticed that it needs new discs and pads.... Front and back. The alloys on my S80 are 18 inches..... And now we come to the part where I'm struggling and really need help...... What are the sizes that I need..... Brake discs... Are they 305 or 320 for the front and 288 for the back... Same with the pads..... And...... Front calliper piston size 57mm or 60mm.... Rear ones 42mm or 37mm??? Now I could just book it into the garage but I want to sort it myself..... Love getting my hands dirty lol.......