Transmission problems on 1997 Pontiac Transport

I’ve got the aformentioned van sitting in the parking lot next to where I work after limping it 90 miles after one of the most worrying drives I’ve ever done. I replaced the spark plugs and afterward the transmission started giving off a rattling noise. It seemed to drive fine besides the noise, so I put off checking it out because I didn’t have the cash for it. Later, I was driving it home and the tranny quit altogeather, the engine would just spin. I eventually got it home, changed the filter, and now it’s back to how it was before. I think the problem with the noise is the torque converter. Does this van require a transmission rebuild or can I do something myself to fix this problem?