Doesnt' take a steel fork to do it (I've used alloy forks with 2kW+ and a really heavy bike); just requires correct mounting of all teh axle hardware, including the torque arm--there's a number of ways to put stuff on but they won't all keep teh axle from spinning.
But it is easy to break them when it's not installed right.
I recommend before you continue that you look at this thread,
https://endless-sphere.com/forums/viewtopic.php?f=2&t=26444
where there are posts showing and describing various issues mounting different types of torque arms / axle hardware.
There are many other similar ones if it's not enough:
https://endless-sphere.com/forums/search.php?keywords=torque+arm*&terms=all&author=&sc=1&sf=titleonly&sr=topics&sk=t&sd=d&st=0&ch=300&t=0&submit=Search
As for the fork, you could replace it with the same model and it'd be fine, once the hardware is mounted correctly and tightly.
If you want a different one, you need one with the same height, rake/dropout offset, etc, so it doesn't change your riding geometry. Also needs the same steerer type and size (and has to have a steerer at least as long as your old one; longer is ok as you can cut it).
Knowing what year/etc the bike is might help a bike shop find the right one for you, but they could also get that information from the original fork.
FWIW, none of the steel-lowers suspension forks I've ever worked with were really useful as suspension; they did make bad pogo sticks
and were ok at making the frontend heavier. The steel-lowers RST Omni on my old DayGlo Avenger bike were easily bent/stripped out when I didn't have proper torque-control hardware; so they're not really any better than the alloy is without that.