If its in good condition, and if its the anniversary model (Convertible), its worth more stock since it was a limited edition car. If its not the special model one, best place to start is with teh suspension and chassis bracing. Itll make it handle better and safer all at the same time. Start with sub frame connectors, then Eibach prokit springs and some sort of performance shocks/struts like Tokico, KYB, Bilstein, Koni, etc. and a panhard rod.
As for more power dont waste your time or money on the explorer setup just get teh better stuff. Like TFS hi-port or AFR 185 heads, a nice cam, a good intake and exhaust. Then get it tuned and watch the f out, itll be quite a bit faster.
-P.