You're fine, It looks like a nice little dozer,
dont worrie about the water in the the fluids, change 'em and run it a few hours and keep changing them untill fluid isnt milky colored.....if its not milky now dont worrie about it tommorrow
we've had machines flooded before and no big deal, the only time i worry is when sandy silty water gets higher than the turn table on a excavator.
and as far as the motor
.....if she aint knocking you're fine there too..... you could sample everything but it's almost guranteed that it'll come back some sort of water contamination,....the guy isnt hiding the fact that she's been swiming, save your money from the sample bottles and buy a case of beer and go play on the new little dozer
as far as the LGP thing goes.....personally I dont like them due to internal pin and bushing premature wear but we are typically a little rockier than you guys up in IA, But remember you arent buying it new and if you get a good deal what does it matter just buy what you can.
I know you didnt ask about price but check out machinerytrader.com on the AUCTION results and see what a comp machine is selling for dont just base your price opinion on what they are listed for sale for on the MT website, I have seen tons of machines on there for well over a year.
Pj