A lot of good things going for it: 03 is before Cat had to pollution up a good engine. Many 03 Monaco had only a 18” deep L R slide out. With only one LR slide the Girard awning is much longer... more covered outdoor area. No window over the head of the bed... not cold in the winter and less noise from your neighbors. Not sure the TV is big enough.
With the Jake brake the brakes should still be in good shape...easy enough to check visually.
Often the slide awnings can be re-sewn as the fabric is still good plus there is enough unused to even cut the used portion off.
Check the bottom corners of the slides for separation and rot. Right angle plates available if separation only.
With good maintenance records and oil samples I would not worry about 150K.
Here is a recent thread on tires that would be worth reading although it has different options on putting a 315 tire on a 8.25” rim. With no front steps, clearance should not be an issue plus with only one front slide, weight should not be an issue... weighing is always a good idea once loaded up for travel.https://www.irv2.com/forums/f115/tir...de-489976.html