The hassles start with having to change the intake, which drives changing the throttle body, which brings up the problem of adapting your old throttle position sensor and wiring the Idle Air Control. I don't know if the injector rail will swap and if the vacuum ports are the same. All in all, it would mean a bit of work. Personally I don't think the gains would be worth it, but that's personal preference. The biggest difference in power from the Renix and the HO lies in the cam, computer, throttle body. The head does flow a bit better but for crawling, that will actually hurt your bottom end while helping the higher revs (highway).
Maybe others can chime in, but I have driven both and really don't feel that much difference between equally maintained motors.