There are already several lawsuits in the pipelines. Ave Maria University, EWTN, Christendom College, several other Catholic institutions as well as a few Baptist institutions.
Which conservative legal groups are fighting this?
Suing against future mandates is very hard to get into court because of lack of standing. Worse yet, they haven't officially written the rules, just this PR stuff to bait Republicans to divert voters from economy and gas prices.
I believe the PR of cases in court between the Church and Obama (Obama-care) would be very embarrassing to them. But that wont happen until after the election.