Concentrate first on getting to know the boat: all it''s parts, features, is everything in good repair to start with, go over every inch of it. Then go sail it and experiment. Don''t just sttle for a comfortable reach; get on a point of sail and see what happens when you tighten or ease the main sheet, what if tighten or ease the jib? both? On a relatively calm day without much traffic, try sailing without the rudder with sail trim only.
All the while, be reading. Of all the books I''ve read about racing, I''d start with Dennis conner''s (with Michael Levitt) Sail Like a Champion. It starts with what makes a boat (materials, fast shapes, movement through water), discusses sails (materials pros and cons, shape,), what is important about boat speed (e.g. pointing highest is not always fastest), the role of each crew member, sequence of crew actions for basic maneuvers (what each crew does when while tacking or jibe-setting), weather, strategy vs. tactics --- the whole shebang.
If you''re really serious about winning, see what you can do to speed up the boat: fair the bottom and foils (caution- do this right, wrong can really bugger things up), get the extra weight off (within class rules); buy good new sails and read the tuning guide (stay tension, jib leads, rake, etc.)
Find a tuning partner - someone with a J40 also interested in getting better. With two boats fairly evenly matched (class rules), three boats is better, sail together on different points and see the effect of changes. Code the fast settings for different wind strengths. Conner discusses how to go about this.
Race as much as you can. An evening sail with your wife is something you both should enjoy frequently, but there''s nothing like racing to help you learn about sailing because you have to go to specific points, in traffic, against the clock.
This should get you through the first six months.
Later on, when you get comfortable with your boat, start working on tactics and strategy. You''ll have learned a lot through experience, but a good read can be a shortcut. Gary Jobson and Tom Whidden (America''s Cup tacticians) teamed up to write Championship Tactics, but I found it requires a pretty good foundation, by this time you should be ready for it.
As for crew, in general, most yacht clubs have a ''crew'' list; ask around about who is good. Other owners, especially the top ones in your area, are a good source - for example, the club is hosting a J Fest but there''s a Schock 35 or T10 owner who is willing to trim the main, or serve as tactician.
Let me know what area you live in and I''ll see who I know in that area that may have better ideas what crew resources are available.