It may be impossible to disassemble the ISS and replace the bad parts in orbit.
Why? You have EVA access to all external parts of ISS Alpha. You should have access to all internal parts of the station. The real issue I've seen come up is all about seals. The station is mostly modular, single piece segments attached to a node. Just seal up that node junction internally (like it was before the module arrived), disconnect external connections, use the station arm to pull the module free, replace the seals, reconnect.
I can think of at least a Lego and a car analogy, but I can't be bothered to type it all out.