Got my first diesel, anything important I should check out on it before it becomes a problem?

Just picked up this 2013 f350 king ranch 4x4, it had 270k miles on it, previous owner did arp head studs, copper head gaskets, rebuilt the transfer case, and "went through" the transmission at roughly 200k miles, the truck is deleted with a 50hp work tune on it as well. It's got some rough up and down shifts, but it sounds like that might be a valve body??? My dad's a big cummins guy so he's not very familiar with anything but that, I feel like I'm somewhat mechanically inclined but never working on or owning a diesel i don't feel super confident just tearing into things on it just yet.

Just picked up this 2013 f350 king ranch 4x4, it had 270k miles on it, previous owner did arp head studs, copper head gaskets, rebuilt the transfer case, and "went through" the transmission at roughly 200k miles, the truck is deleted with a 50hp work tune on it as well. It's got some rough up and down shifts, but it sounds like that might be a valve body??? My dad's a big cummins guy so he's not very familiar with anything but that, I feel like I'm somewhat mechanically inclined but never working on or owning a diesel i don't feel super confident just tearing into things on it just yet.