RPG and XML or JSON

Hi,

I need help to decide if the YAJL Open Source JSON Tool is the right
choice for us.

I'm working on a new application that will accept and return data in JSON
format.
The company that will be sending the data already receives it in XML format
from their client and converts it to JSON that it sends to us. Then, on
receiving our JSON response, it will convert it back to XML for the client.
We are currently only used to dealing with XML formatted data only and have
no JSON experience. We have a couple of possibilities that would enable us
to convert the data from JSON to XML and back which would be a shame to
have to do.

We need to weigh up the cost between implementing a solution that we know
how to do and one that we don't but looks better.
How can I go about estimating the time to install and deploy the YAJL
solution? Is it an easy solution to implement?
Is there any way of estimating the effect on the response times if we were
to convert the JSON to XML? That would mean 4 conversions of the data from
XML to JSON and back.

Thanks!