I have my dash apart right now. I used a narrow putty knife to release the velcro. It takes a little wiggling and several passes with the putty knife to get it loose. I also crawled under and cut several tie wraps to create some slack in pieces of the harness.
My wiper motor is accessed thru the generator panel on the nose.
Actually, open the hatch and let more light into the space. Crawl under and sit up and work on it.
You cannot access anything under the dash.
My wiper controls are in the steering wheel.
2003 Tradewinds LTC, Dynomax Chassis,
350 Cummins, 2008 Lexus RX400h, 18' PJ Trailer