91 Automatic Transmission Issue, won't engage Options

[bachlauter]

hey...noob here!

Ok...I got a transmission problem that has gotten worse over time. Slowly but surely it has nearly stopped engaging completely. Forget about driving up hills!
At first it seemed like you were always starting out in second gear...the engine would revvvv and you could only get it to crawl. Occasionally it would work and you'd take off from a stop sign like a rocket!
Now it barely crawls...It's really not drivable.
SO the question is....should I try to find a used tranny? A rebuilt tranny? Or try to get my current tranny rebuilt?
Has anyone gone thru this? How much for option three?

Also...I believe it is electronically controlled...any chances it's a simple fix? I know the PO pulled a boat around with this truck. EEEEEEEEEEEEEE
(it has about 120,000 miles)

~Christy