Welcome Olaf
A bit of generic information for you, I have no personal experience with that model machine.
1. Remove all the wheels, Right hand thread on the right hand side and left hand thread (probably) on the left side, the LH thread comes off by turning it clockwise looking at the nut (opposite to normal) Clean any rust or dirt off the shaft.
2. take the belt off
3. Undo any screws holding covers or guards over the bearings.
4. Some machines have bearings that are held on the shaft by grubscrews, if that's the case undo the grubscrews, also may need to undo grubscrew holding pulley on the shaft.
5. If the bearings are not held on the shaft with grub screws then it will be a press fit and the bearings will need to be pressed off in a workshop with a press. So you will need to remove everything you can to get the shaft to the workshop.
6. before taking the shaft to the workshop call into your local bearing supply place and buy two bearings, they have a number on them and usually will be just an off the shelf purchase, they will probably cost $10-$15 each, replace both, no point doing all this, putting it back together and having the other bearing give up in two weeks.
7. Find a light engineering place, even some garages will have a press, get the bearings pressed off and the new ones pressed on. Do not be tempted to belt it with a hammer and do it yourself, you WILL damage the shaft.
Hope that helps.