In case you have a Juno-6 some drilling is needed to install the midi sockets. For a Juno-60 the DCB panel can be replaced with a custom midi panel which you can order as an option.How hard is the juno 66 mod to install? Does it need much cutting of panels etc?
Desoldering the original CPU might pose a challenge depending on your solder skills. See the installation manual for various ways to do this.
Juno-66 can of course also be installed by a synth tech in your area: