If the engine is'nt any good, I would swap a diesel into it. Kubota 2203 is what I was planning for mine until I sold it. It is no secret that the 1830's where under powered. All agree another 15 hp would be perfect. If you have something else in mind of simular power, it'll probably work. My opinion is that diesels are just better suited for the work the skids do. The work for the swap is usually the same regardless of what you stuff in the hole. Why not make it more appealing if you need to sell it? Popular engine= easy to find parts.
A very small amount of metal is probably just normal wear. The water may be a bigger concern(rusty tank) When my 1830 lost a drive pump, I found probably a quarter cup of Chunks in the right tower. Your probably OK. All of the hydraulic returns run into the right tower, all of the pump pick-up's are in the left tower. It is very rare that metal makes it back to the pumps for this reason. A very good design I might add. The chain case is seperate from the hydro's. That's another 5 gallons of bulk oil. In the future, you can use you hydro oil you remove on a service and put it in the chain case. The chain case is accessed by raising the lift arms and removing the covers on top of the chain cases. Pretty easy if the machine is running to raise the arm's. Not so much if it is'nt. You can either unbolt the lift cylinders and lift the arms, or lift the arm's while someone holds the lever's open so the hydro's arent locked. Use the lift arm lock when it is up. The drive chain can be found at any farm supply store, so don't freak out if it needs all of them.
No, the chain cases arent connected.