I'd wait until you can drive it in dry weather - it may not really be a problem.
Check that tire pressure, diameter, and wear is fairly equal.
Nose dive can be caused by the fronts braking harder that the rears, or the rears not working at all.
This may, or may not be relevant. Making the rears work like they should.
Here's from 3/18/10 entitled "nose dive":
It could be the rears weren't adjusted properly. It's important.
The rear shoes have to travel a little before they touch the drum. The "hold off" valve in the proportioning (combination) valve can only do so much. Too loose in the rear lets the front discs do all the stopping.
When adjusting with the E brake - back off the E brake cable so it's loose. Then adjust the linings. Tighten them until the wheels won't spin or spin hard. Have someone step on the brake pedal, then release. Notice it may not now be tight! If the shoes weren't centered, they may have been dragging making you think they were tight. Keep doing it till stepping on the pedal doesn't make them loose again - now they are tight!
After it's tight, back off 2 or 3 clicks, it will still feel tight. Step on the pedal and release - that centers the shoes again. Wheel spins OK now? If not, do it again, then step on it again.
Important -- Have the helper step on and release the pedal after every little bit of adjustment. - that keeps the shoes centered. Otherwise you'll get them too loose.
After the wheels are properly adjusted adjust the E-brake cable to take up the slack but not pull.
Seems like adjusting drum brakes properly is a lost art.
It's possible by not doing it like that you have the shoes adjusted out too far - then the shoes don't make contact until long after the fronts do the stopping == giving you the dive!