Do I need to purchase engine oil and hydraulic fluid from the dealer or can I purchase from a more reasonable priced source?
So long as you buy a reputable brand of lubricant there is no reason whatsoever to buy fluids from a Cat dealer. Something like Conoco, Mobil, Shell, etc, would be fine. I'd guess in your climate you'd probably be looking at something like 5W/30 or 10W/30 (depending on how cold your ambient temperatures go) for the engine and 10W for the hydraulic system.
Thanks.
Nige knows his stuff, I agree.