Hey Reloadit!
If the car is running good you should be in the clear, headgaskets were the killers on these cars and I don't think you will run into that if you run into that if you just drive her easy. To save yourself the hastle of repacking grease and redoing CV boots, I would recommend replacing the whole axle. I ran into that exact issue on my previous 05 OB 3.0R. Grease from the inner CVs was leaking onto the cats causing a burning. I replaced both of the axles as a whole. It seems pricy at first but usually NAPA can give you a decent price. Just make sure you bring back your cores! However if you are pressed for paper, you can totally just do the boots, but I would do both sides to make life easier down the road.
For tires, heres kinda my top picks.
1. General Grabber AT2
I had these on my 2005 Outback and they killed it in the snow and were pretty easy going. They were also silent and rode great on the road.
2. Yokohama Avid series
Not very off-roady but still great in the snow,dirt and anything you throw at them.
3. Bridgestone Blizzak
Yes, it's a winter tire but they do great on dirt from what people have told me, pretty affordable too. Also can't go wrong with a bridgestone dualer.
(coming from a tire tech)
As for the tire pressure, I would run maybe 33-34 during the colder months but during the summer anywhere from 31-32 is gonna be your best bet!
Cheers!