98 Windstar transm. won't move :( ???

We have a 98 windstar. For a few months there has been a bump in the 2nd gear. For the last month the van would slowy decend from drive way in reverse, while I would push on the gas and rev up. Then it started to do the same in drive. Today, on the highway it would only very slowy increase in speed when reved high. It stopped in a parking lot, and cannot be moved. It doesn't matter how much I rev it up it is not budging. We have not changed the transmission filter since buying it in 03. The transmission fluid level is fine. What are the chances of this being a minor problem, vs. needing to rebuild? If it's just the filter would that have anything to do w/ the bump in 2nd gear?  Thank you.

I feel your pain.   At least you got some warning.  My wife was suddenly stranded by the same problem.   I told my Ford Dealer about my 2nd gear observation over a year ago  and they said they could not find anything.  This week at a traffic light it just wouldn't move.   Regarless of what gear she tried, no power would pass from the engine.   I check the fluid level (ok). The gear sellector linkage had to be ok  as it would still go into park.  ( Had a problem with an old Astro Van the linkage slipped and wouldn't stay in park).   Got it towed.   Mechanic said it was gradual wear of the hydraulic pump splines to the point where it now slips free from the pump gear.  He suggested the spline shaft wasn't tempered properly when built.  In short total rebuild.    105,000KM (63,000Miles)-just out of warranty.  I can't tell you how much it cost because when I bought my van from the dealer I paid an extra $1,350.00 for extended warranty   so I guess I paid for my repair in advance.
 
good luck.