Answers

You definitely should not have any leaking.  I suggest you call a plumber to come look at the issue.

I highly recommend getting the opinion of a local arborist.  If you have trouble finding one check with your local tree nursery or Botanical Garden for a referral.  We have used one before and it was the best $100 we could have spend considering the situation.

The materials are just 30% of the cost.  They are labor intensive and if you are fairly handy you can save a bundle of money doing it yourself.  However, this is not a task for the average DYI.  If you hire someone to supply and install the system you can plan on spending $3,000 and up depending on the size of your closet.