Personally, I love taildraggers and don't fly anything else. They are a great way to get your left thumb involved in flying.

To convert your Seniorita, you will want to reinforce the fuse in the area where you attach the main gear. The attachment point should be such that the wheels are located somewhere near the leading edge of your wing. There is some wiggle room in the exact placement, but this should get you pretty close and with a plane like the Seniorita, the placement should not be too terribly critical. As far as the track (distance between the main wheels), try to keep it the same as your trike gear or at least pretty close.
There are several commercially available tailwheel units available. I'm partial to Dubro's but Sullivan also has a good reputation for light weight and durability. They include instructions for installation, but are fairly simple to figure out.
I'm sure you'll get lots more detailed information, some of which may differ from my thoughts, which is fine. There is (almost!) always more than one right way to do something.

As my dad used to say, "Remember, free advice is often worth exactly what you paid for it."
Darn typo!