First and foremost, you may have trouble getting your loan approved.
I recently worked with a buyer who was buying a townhouse whose association was in litigation with an ex-employee. The HOA was not cooperative in releasing any information (even though, FYI, most litigation details are public). The other agent and I worked tirelessly to obtain documentation since Fannie Mae refused to underwrite the loan until we received specifics.
My client's closing was delayed 2 months! We were finally able to close, but only once we were able to provide all of the required documentation to the lender for Fannie Mae -- which we finally were able to get only once we were in contact with the HOA's attorney, who finally agreed to cooperate.
Before you even concern yourself with the details of the actual litigation, I would check with your lender to find out if a litigation will affect your ability to get a loan. Find out precisely what will be necessary in order to have your loan approved.
After that, your Realtor can work with the other Realtor to get the association to cooperate. Perhaps using the same route we did (contacting the attorneys) will help. If the HOA refuses to cooperate, they can be charged with hindering a sale -- I'm sure it's not something they wish to have on your plate in addition to a litigation.