I know I'm late to this thread but I did exactly this, box purchased from Avionics Source. I had a non-WAAS GNS430 so I had to replace the antenna. Existing coax was good so that saved some labor (as I recall the length of the coax is also important). If you need to replace the coax it means pulling out the headliner, which means pulling out the side panels, which means pulling out the front seats, etc., quite annoying and labor intensive. I had to replace the existing GPS CB for a higher amperage CB, per Avidyne install requirements (I think 5 amp to 7 amp), and this was a horrible job. The A&P spent the best part of the day working on this alone and was swearing the whole time ('78 J). As I was going from non-WAAS to WAAS there was an additional setting on the IFD I had to set to get the glideslope up. I've been flying with it for a few years now and my only regret is not swapping this out earlier. I have mine driving 2 Aspens, which drive a legacy KFC200. Bottom line, it's a slide-in replacement but you could be looking at a couple of day's labor.