This probably indicates a transmission failure, which I do not believe is uncommon for LHSs. Check out the common problems on RepairPal--that may be some help: http://repairpal.com/chrysler-lhs-2000/common_problems
You'll most likely need help from a transmission specialist.
Possibly the shifter itself is bad http://www.parts.com/oemcatalog/index.cfm?action=getJointLocator&siteid=2&chapter=&Sectionids=0,2648&groupid=2649&subgroupid=3604&componentid=0&makeid=7&model=LHS&year=2000&graphicID=NE99290&callout=7&catalogid=2&displayCatalogid=0 Here's a blow up of all the parts for the shifter assembly.
...However, due to the age of these vehicles, mechanical failures are more likely to be causing transmission problems. If a mechanical failure is repaired or the transmission is replaced, it is important to make...