I believe the 4.5 is a closed cooling system with heat exchanger. This protects the engine block from freezing, but the the exhaust system and circulating pump still must be drained. Merc has a "single point drain" system on these engines. But you may want to see what this forum says about that. I believe extra steps beyond Merc's stated process are required.
Pulling the out drive is within the capability of anyone with basic mechanical skills. With a new boat under warranty you could probably pass for a couple years. I'm betting you have an Alpha II, and that is not a man killer like the Bravo to remove. You trim up, disconnect the speedo tube, trim down close to ground, remove the upper steering cylinder pivot shaft. Place the shift control into full forward. Then remove the six nuts attaching the drive to the bell housing. Then pull it rearward, and off. Lots of help here at iBoats if you struggle.
No doubt I/Os are more work than an O/B. They don't self drain, and the drive shaft assembly is complicated, needing regular inspection. But the advantages are worth it, in my mind. Quiet, more fuel efficient, and more usable room in your boat and on your swim platform.