The Mac Studio's storage isn't quite as set in stone as you might think, although you'll want to keep your expectations in check. iFixit has conducted a teardown of Apple's pro desktop that suggests you can replace the SSD module in limited circumstances. The company managed to swap the drive with one of the same capacity (from another Mac Studio) by using Apple's Configurator app to perform a DFU restore.
You can't add a second module in the base model, and it's unclear if higher capacities will work. However, this does suggest you could revive the Mac Studio with a spare module, if Apple ever makes them available through its self-repair program.
It's no surprise you can't replace the RAM, which is built into the M1 Max or Ultra chip. The Mac Studio is easier to access than you might think, though, with Torx screws (albeit a huge number of them) and removable ports. And yes, the cooling system in the Mac Studio is as massive as you'd heard. The fans are larger than on other Macs, iFixit said, and the aluminum heatsink in the base model is six times heavier than the one in the Mac mini.
The teardown led iFixit to give the Mac Studio a 6/10 score for repairability. The non-upgradeable components are the largest concerns, but the repair shop was also concerned about buried fans and the potential for dust build-up. You're probably not buying this system expecting to treat it like a Mac Pro or many PC towers, but those limitations are worth noting if you intend to maintain the Studio yourself.