I Broke my tail installing the fuel tank
grin......... Next time use a shorter fuel tank.
Just kidding...........
Whenever you repair something that's gotten dirty or greasy from use, clean it up really well before trying to reglue it. K2r is a carpet cleaner for cleaning spots on rugs and you can find it in the grocery store. It's great for pulling oil out of wood. Denatured alcohol works slightly better than Windex (which works ok) for cleaning off the coverings.
When you're regluing something like your stabilizer and it's a butt joint like shown in the photo, it's worth thinking about how it stood up to the abuse that broke it. It really might be worth the slight extra effort to put in some extra bracing. After looking at your photos, it looks like there would be room for a strip of triangular stock on each side of the fin that'd glue to the stabilizer and to the top of the fuselage. If you skinned the top of the fuselage back there, and the lower part of the fin, the triangular stock would improve the strength back there a TON. Then cover with a strip of monokote. It's easier to cover than the original joint would be.
BTW, just trimming back the covering at the bottom of the fin and the area of the fuselage around the fin, and then putting a small fillet of epoxy along the joint would increase the joint tremendously. Mix some microballoons into the epoxy if you're worried about weight or your CG.