Don't sweat it!! It happens to everyone at one point of time, and repairing the damage is not as hard as it may appear to be! I'll outline the damage by sections, and techniques from one section can be used for other areas on the plane. The most important thing to remeber is to retrieve all that you can after the crash, as broken pieces can serve as a guideline or even a pattern for rebuilding parts.
If a break occurs in the horizontal or vertical stabilizers, it is imperative to get them fixed. The severity of the break directly relates to the plan to fix it.
This is when the stabilizer is dangling by a couple of wood fibers. The best thing to do here is cut the better part of the covering away and remove anything that doesn't appear to be solid. Then you go to the hobby shop and get some more balsa. Using the broken pieces as a guideline, construct a new section of that particular stabilizer. Now square up the remaining parts on the plane and glue the new section into place. Be sure that the new portion is level (a hobby triangle works good for this) once the CA has cured, glue in some reinforcements (1/2" x 1/4" balsa works well). Now re-cover the new section and you're all set. In some cases, if properly done, this will be stronger than the original structure!!
This is just when the stabilizer is merely cracked or a piece is broken. If you are not concerned with appearances and the break isn't in a high stress area, sometimes you can throw some 6 oz. glass cloth over it, smooth it down and call it good. In other cases, you cut away a small area of covering, glue it together and reinforce it a little. This can actually be done at the field, and a total of 10 minutes flying time is lost!
There really is no "minor" damage to the fuselage, and access is limited. If looks aren't an option, just wrap some glass cloth around the break (most damage is caused when a glue joint comes apart) and epoxy it together. If looks are important to you, and you can access most areas of your fuselage, here's what you can do.
Take the wing (or hatch) off and find the area of the break. Depending on which is easier, you can either glass the inside corner of the fuselage or use my method. My method is to get a 12" (or however long you need it to be) of square balsa and glue it into the damaged corner of the fuselage. You can use CA if it is a small piece, but i prefer 6 minute epoxy for a little more working time.
The key thing to remember here is that you can not repair a damaged firewall. The best thing you can do here is get yourself a piece of 3/8" plywood from the hobby shop and build a new wall. Use the old wall for a template for bolt posistions. One hint is to cut the new one slightly larger than the old one- you can always remove exess, but you can't add to it! Be sure to sand it down to a perfect fit, because the firewall is the most stressed piece in the whole plane. once you get it to fit exactly into the opening, reinforce the fuselage with scrap balsa and glue it in place with 24 hr. epoxy. (note.. if you plane had any offset thrust built into the firewall's mount into the fuselage, you may need to shim the mount in order to offset thrust with the new firewall.)
Who hasn't touched a wing down during a rough landing!?!? Definitely the easiest to bruise, but also easy to fix.. There are many areas to damage the wing, so I'll divide it up..
Hands down the easiest to crunch! However, they are also a snap to fix. If you just crush the tip, but don't damage the outer rib. you can just cover over the damage and forget about it. If you damage the rib, just reinforce the rib with either thick sheeting, or make a "new" rib and glue it over the old one. Not a huge problem!
Sheeting (Top or Bottom)
Like the tips, if there is only a minor brush or a small hole, just cover over it and forget it! In face there isn't much you can do to repair sheeting, and if there is enough major damage to the wing surface (ribs, sheeting,etc...), you might as well build a new wing or a new plane.
The Mount Plate
This is a little tricky to do, but can be the key to salvaging a semi-totaled plane. If you rip the mount out of the fuselage, build another one. Keep in mind the room it takes for servo throws and your spacing for the mounting bolts. The best way to build a new mount is with 3/8" plywood. When installing the new mount, it is best to reinforce the area (especially if the fuselage is made of balsa) with thin plywood (1/8") Use 24 hour epoxy and make sure the bolt holes line up properly!!!
If you damage the mounting holes in the wing itself, you may be up a certain creek without a paddle! If there is a way you can alter the mount in the fuselage and make a new hole in the wing, that is the way to go. A good tactic for this is to change blind nuts in the fuse mount plate to meet the size that the new hole in the wing would provide a match for. If the mount in the wing is too damaged, you may be better of investing in a new kit.