Look in your maintenance guide and see what is required for the 30K servuce. Assuming that you have been keeping current with the maintenace so far, my '97 maintenance guide lists the following items under the severe duty schedule for 30K service:
1) Change engine oil and replace oil filter.
2) Replace air cleaner filter every 50,000 km (30,000 miles) or 36 months.
3) Inspect engine cooling system, hoses, and clamps; check coolant strength every 24,000 km (15,000 miles) or 12 months.
4) Change fuel filter (Recommended but not required for California Certified Vehicles).
5) Inspect and lubricate automatic transmission shift linkage.
6) Inspect disc brake system amd lubricate caliper slide rails.
7) Inspect drum brake systems, hoses and lines.
8) Inspect and lubricate front wheel bearings.
9) Inspect parking brake system for damage and operation.
10) Change transfer case oil (4x4).
For the price they are chargeing, it sounds like they are doing a lot more than what is called for in my manual. Either that or their labor rates are outragious.