Its very easy to do, takes about 20 minutes including a cup of tea
You will need barrel, probe assembly and of course a .22 mag
Best way is too buy the barrel off the sales section, they often come up, probe maybe too, new 12 shot mag costs about £50
You will be able to recoup some of the expense by selling your .25 kit
When/if you are ready to go ahead with cal change just ask on here and we will talk you through it
Baz