Jose...Converting a ketch to a sloop is not a good idea from a sailing perspective because the main mast will be in the wrong place and the balance and sailing characteristics of the boat will be negatively affected...particularly with a larger mainsail. You will also probably degrade the value of the boat as a consequence.
Nevertheless...if you do go ahead....the two systems that consistently get good reviews are the Shaeffer and the LiesureFurl. I have the Schaeffer on my 52 footer and am very pleased with it. Understand that the system + thenew mainsail required will run you over $20k with the Schaeffer and the Leisure furl is slightly more expensive. This is WITHOUT an electric
winch which is pretty much needed as well which will set you back another 5-8k installed as well.
Anyway...there's a few things to think about...Welcome aboard!