I would certinaly replace the batteries for all Tx and Rx. It's not worth the risk of having a failurein flight due to an old battery. I replace mine every 2 years regardless of condition.

If it were mine I'd send the Tx and Rx in for service to either Radio South or the manufacturers service dept. Horizon checked out my Tx and Rx for $30 including return shipping after an 8 year break from flying R/C aircraft. Can't say it's really worth while, but it made me feel better.

Certianly check the heli over very well to make sure everything is tight and what is suppose to move still moves freely. If you have wood blades I would consider replacing them as well or at least strip the covering off and check the glue joints and such.