I've dove the Duane a dozen times or so. If the current is truly dangerous, the dive operator will cancel the dive and go somewhere else. From your profile picture, you look like you're in pretty good shape. I've dove the wrecks in Key Largo on occasion where one had to use a fair amount of upper body strength to pull oneself along the granny line and then down to the wreck on the mooring line: just don't kick your feet and only pull yourself hand over hand on the lines so you don't blow through your gas too quickly. For someone in decent shape its not a big deal. Once you get down to the wreck, you'll be able to get in the lee side of the current on the wreck's structure and enjoy the dive. You'll be flapping like a flag during your safety stop, but again, not that big a deal.
I've also dove the Duane when conditions were completely calm and I was able to simply float down from the dive boat without touching the granny line or mooring line.
Aside from underwater conditions, February can be pretty bouncy on the surface too. When dive boats are jumping around, I like to dive with operators that have christmas tree ladders that allow you to climb back on to the dive boat without taking off your fins. I know Conch Republic and Silent World both have these type of ladders.
I've never hired a guide, but it might be worth it if you want to find the cool swim throughs. There are some that I didn't find until I had a half dozen dives on the wreck. The Bibb is also an interesting dive, but deeper and the ship is a sister to the Duane. If the dive operator gives you a choice of a double dip on the Duane or one on the Bibb and one on the Duane, take the double on the Duane.
I'm sorry to hear about your brother: I hope your dive brings back some nice memories.