I have a ASA upgrade, where a 5520 ASA configured for transparent is currently supporting EIGRP with only ACLs - permit eigrp ..... source destination (host 18.104.22.168) - the replacement 5550 ASA will be configured for routed mode and a "router eigrp AS" process will be applied. Once an ASA is configured in routed mode, with an EIGRP router process enabled, how is the firewall configured to support EIGRP?
"so, even though there are numerous ACLs assigned to, let's say, both the inside and outside ASA's interface, there no longer is the need for "permit eigrp source destination" ACLs?"
Correct, because in transparent mode the EIGRP traffic was passing through the firewall whereas in routed mode with the firewall running EIGRP this is no longer the case ie. the firewall is now an EIGRP neighbor.