Do I need new refrigerant oil and freon after swapping in this condenser?

Your AC system will need a full evacuation and recharge. Moisture and debris inside the old lines can damage a new condenser, so flush the lines before installation and have a shop pull a vacuum on the whole system before adding fresh refrigerant and PAG oil.

Does this condenser come with new O-rings and seals?

The condenser assembly ships as-is. Pick up new O-rings and seals specific to your Sprinter's hose connections — they're inexpensive and prevent leaks at the connection points.

Can I install this myself, or do I need to take it to a shop?

Removal and mounting are straightforward if you have basic hand tools and a lift or ramps. The refrigerant work — evacuation, flush, recharge — requires EPA certification and proper equipment, so that part needs a licensed tech.