503 Galion hydraulic fluid filter

Brought this one back from the dead need some help anyone know where i can fined the correct filter for the hydraulic tank also the best manual for it, plus fluids , what type of grease should i use I is a nice unit and would rather do preventive maintenance then have it brake when i need it
serial no 503-HDC-05690 if you have any info on it let me know
I also did did a motor transplant in it it had a d-236 or d- 282 soif you need parts for your let me know