Jmac,
Though not intimately familiar with a 99, I believe staying with 15's is a money move. For future flexibility, 15x8 wheels are a good move but if you know that your going to go bigger a nice set of 15x10 wheels will look great and accommodate most any future tire upgrade.
I originally bought a set of steel 15x8, I still have them, their strong, strait but look like poo. I have since come to own two sets of Aluminum 15x10's and I really like what they bring to the driving experience ..)
Either move can work well, my used set of steelies cost $50, so the value is very hard to beat.
As far as tires go, if your still in VA and planning to off road I like these;
Interco Super Swamper TSL Bias, SAM-12
I used to be a died in the wool radial tire fan but these past 16 years I've had nothing but bias plys and really like what offer to the driving experience. They just seem tougher and feel better driving on.
The Interco SS TSL Bias is well suited to abuse, wet, snow, dirt and mud. Sand...not so much. They will hold their tread a long, long time.
Despite my Interco speel I am currently using Mickey Thompson Baja Claws for wet and Baja Belted for dry; where I live, the belteds are almost a liability, unless I'm in the dunes, then, they are KING!
I had a very good experience with a set of Pirelli's Radials for primarily road driving; the set has over 80kmi on them with only approaching half tread depth worn. Their rubber compound is perfect for cool/wet, translation, the Pacific Northwest.