89 Stanza auto trans/speedo problems

I just bought this 89 Stanza cheap from a police impound auction last night, and noticed two things on the way home.

1.) The speedometer doesn't work. Tach works, speedo out. Is it cable or electronic? Where do I start troubleshooting?

2.) Auto tranny shifts back and forth between third and overdrive. I noticed when inspecting prior to auction that the tranny appeared overfull. Could this cause it? Other causes?

I'm mechanically inclined, so feel free to go into detail, here or in an email.

WANTED STUFF (please email me):

1.) Service manual.

2.) Left rear exterior door handle.

I need to get the kinks out of this car so it can do a daily 50-mile round trip commute. My other vehicle is an F150, and this Nissan will save me $2,000 in gas a year at $3 a gallon. Typical Nissan, the a/c still works!!!

Thanks!