Hydraulic Power Assist Steering System problems of the 1999 Volvo S80

Transmission problems causing dangerous driving conditions. The transmission slips when going between 2nd and 3rd. Also had issues with the engine going to 700 rpms when going 65 mph. This is just one of the many problems. The solenoid went out in the transmission about 13000 miles ago. Currently I have three different error codes "transmission service urgent", low oil pressure stop engine ASAP", and "emission service required". I have read many other people have the same problems I have had. Nm.

1) p/s unit failed allowing p/s fluid to rapidly drain out.

Vehicle message center displayes: abs system failure/servicing transmission system service power steering service emissions control service also, there is an engine oil leak and a tie rod replacement/four wheel alignment was required cruise control is intermittent directional signal inop headlights come on when not commanded etc. Incident date--throughout ownership .