Where exactly is the leak? Any pics or can you better describe where it is leaking?
Doing the LIM gaskets on a L67 SII 3800 engine is a DIY job. Just tedious if it is your first time. The procedure is the same as the N/A SII 3800 engine except you substitute removal of the Eaton M90 supercharger versus the plastic UIM plenum found on the N/A engine. Be sure to get good quality supercharger and LIM gaskets and follow the proper torquing procedure for all SC and LIM bolts.