I was hoping to get some advice on how to maintain these outdoor wooden stairs and walkway. The topside is looking quite bare compared to the underside and I'm concerned about rot or splitting which could damage the integrity and pose a serious safety risk if left untreated. I am not a DIY expert but hoping this is something I can do on my own with the right products. Thank you in advance for any advice!
Welcome to the Bunnings Workshop community. It's fabulous to have you join us, and thank you for sharing your question about maintaining your wooden stairs.
It looks like you've caught it just in time, another season of exposure and your unprotected timber steps would probably have started to deteriorate. Although it looks like all the protective coating has come off, I suggest sanding the surface with Flexovit 115mm x 1m 180 Grit Painted Surface Sandpaper Roll to make absolutely sure that it is prepared for staining or sealing.
To shorten your sanding time, I suggest investing in an electric sander, it comes with a series of graduated pads that's perfect for your project.
Your wooden steps and your timber walkway are like decking panels that must be protected from the elements. It's number one enemy is UV exposure, even a single coat of stain is enough to protect the timber surface from exposure. I propose having a look at Intergrain 4L Merbau UltraDeck Timber Decking Stain. It is suitable for use on all exterior timber including decking, cladding, doors, window frames, screening, fences, garage doors, walkways and weatherboard.
I suggest visiting your local store and having a look at the sample stain board in the paint department. You'll be able to see the different types of stains and sealers available. Once you've made your choice the paint specialist can help you estimate the quantity you'll be needing to cover the area.