Do I need a dedicated IPN? Do I have to change IPN settings in my PayPal account?

No. Even if you have a dedicated IPN for something else, E-junkie service will not be affected by that as E-junkie's buy now and cart buttons already contain that setting for products being sold through E-junkie

The only time we ask you to specify our IPN URL is when you are selling on a site like eBay where you can not use E-junkie purchase buttons to initiate the sale.

• Questions?
  Feel free to contact us if you don't find an answer in our Help pages or our Forums.
  
  If you just want to enquire about what all E-junkie does, you can check our feature list.