Harbor Freight sells a decent ball joint service kit that also includes things to press out the universal joints. I have owned it for about five years and used it about 8 or nine times. It was around $40 when i bought it, not sure what it costs today but it (for me anyways) has been worth the money.

Also, to add to Sooper's post.... Having good universal joint also keeps everything tight and inline... that leads to less stress on differential parts that can end up costing you a small fortune in the end.

 

A socket and a hammer will work of you don't have any of the special tools.

 

That's how I was taught too. A local machinist showed me that a hammer and punch are far better than presses because you never have to worry about bending an ear. The impact is also better at breaking corrosion when pushing out the old joint and as long as the bores are cleaned up good before the new joint the caps hammer into place perfectly.

Remember, check for binding when installing the new caps. You want the rotations to feel smooth and 'secure' but not too tight where you have to work to get it to actuate.