Have some quick questions for all you Chrysler gurus out there..

I own a 98' Sebring convertable with about 65k on it. A couple months ago when it started to get cold I noticed at random red lights my rpms would sometimes do a little dip and when the light would turn green i would push the accelerator and the car would feel like it wanted to stall. It would clunk forward a little and sputter sputter sputter but not quite clonk out. After a few beeps from behind i would floor it and it would go on as normal. It wouldn't even do it again at the next red light. I brought it into a garage and they told me there was a loss of pressure and they changed the head gasket. I haven't noticed any problems until a couple days ago when it did it again. I know this could probably caused by a number of reasons but has anyone had a similar problem with their sebring? Im about to bring it back to the garage but wanted some input so when im there this time i dont get jerked around =\

Next question is...

Has anyone ever had any problems closing their driver side door when its really cold? In the mornings here in NY it gets pretty cold and sometimes cant get my door closed unless i slam it shut with all my strength. Just the other day my door flew open on a tight turn and almost hit another car at an intersection. I've lubed up the little black thing inside the door (the little thing that latches on to the loop on the inside) and when it warms up it mostly closes normally. Anyone ever have that thing replaced? any quickfixes i should know about or the price range on a replacement?