Firstly lock barrels come in kit form with numberd lock discs [usually six ] which can be inserted to match your existing key you will have to tell them at time of ordering you want one made up to the same as your existing key code. Secondly I don't consider you need a new lock.
Over the years and cars I've had I've worked on most of the locks for one reason or another. Lock barrel turning!! yes that's 6 I've done it's the lock barrel retaining disc or grip washer come loose.
It's a bugger of a job as obviously means removing the door panel to get access to the back of the lock. Usually screws behind the match caps covering the screw holes in door handles,window winders [if manual] arm rests and bottom of door storage areas [some are moulded in the panel] and lastly under the door. check the areas again then eas door panel off clips.
The hole the lock barrel fits through has a cut out in it and the lock barrel key collar has a lug on it that fits this cut out. On the back of the lock is a pressure washer when pushed against the direction of the key along the barrel tightens the lock barrel into the hole and cut out so it doesn't turn. Or it's a threaded collar [does same thing] that's come loose and needs tightening. firstly put the key in the lock and push against the barrel turn the barrel slowly until you feel it drop in the cut out. Then lock then wont move any more. At the back of the lock is either a grip washer or threaded collar which has come loose Just push the grip washer back along the lock barrel hard against the door frame and lock front to tighten the barrel. Or if screw collar type then screw the collar up tight against the lock front.
Hope this helps.