Welcome redeldo to the Newmar forum.
Would start off by saying a Newmar you should be happy with the items you have listed are in need of maintinance. Tranny fluid could be Transynd synthetic check for a sticker around engine compartment or in the papers you may get with coach.
Mileage is good as long as they kept it up and tires should be ok if driven alot.
Oil leak could be just the drain **** not tight and check time used plus oil , air filter. If it was used alot thats a plus.
Good luck in your hunt and tell them you want a HDLCD.
Some DP owners will be on here for sure to help you out.