It's probably due for a new timing chain, guides and tensioner at 150,000 miles unless you have records to show that it's been done.

The only tool you need to replace the blower motor is a screwdriver. A new motor without cage can be purchased from FastLane for under $110. I wouldn't rush out to buy one without making sure it's not a bad push-button unit or blower resistor pack that's keeping the blower from turning.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD