This is a total judgement call that only you can make; it all depends on your circumstances and the real damage to the vehicle. From my experiences, if you are not capable and willing to do do almost all of the work yourself, you should quit while you are ahead and move on. Things like wheel alignment, should be done by a pro with the right equipment.
Questions you need to ask yourself:
1. What is the vehicle worth now v.s. what is it worth repaired. This is actual resale value that if you have a salvage title won't be an easy sell. (write down some realistic numbers for comparison and leave out emotional attachment)
2. What is the vehicle worth to you; assuming you will actually drive it another 100K to 200K miles to the point where it won't have more than scrap value when you are done with it.
3. Do you have a place to work on the vehicle; the street doesn't count here?
4. Do you live near self service junk yards? You can learn a lot about how not to take things apart and a lot about how your vehicle is put together at these places as well as get in on bargain days when they reduce prices. Be careful of the shady people that sometimes lurk around these places and call themselves mechanics that offer to help you for a price. Here is a link that shows a bit about these places:
Down On The Junkyard The Truth About Cars
5. If self service junkyards are not available to you, check the standard junkyards and get some quotes from several yards. If they send off to another yard for parts, there will usually be a much higher price than if they pull it off one they have on their lot. A number of these yards are rip off artists; be careful of leaving a deposit that isn't 100% refundable if you are not satisfied.
6. How much are you going to spend on new parts. Things like brakes and universal joints are not worth trying to get from the junk yard. Rock Auto is your friend here.
RockAuto Parts Catalog
7. How much are the parts going to cost you to fix it? Write down twice that figure for all of the hidden things.
8. What is your time worth and how much beer will you have to supply your buddies to help you. Believe me it will take three to four times as much time as you first expect.
9. Are you going to paint the vehicle, assuming you find all of the body parts? Call some places that paint vehicles for some pricing. Face it you are not going to put a $3000 paint job on an old Previa.
Auto Body Repair And Painting Maaco com
Earl Scheib Wikipedia the free encyclopedia
10. The vehicle will definitely need a 4 wheel alignment before it is fully functional. Other things to consider are how fast you need the vehicle, what your state requires for inspections etc., what is required for registration etc. and will your neighbors complain about your yard looking like a junkyard.
11. Do the math and be realistic about it. Is it worth it to YOU?
12. Alternatives to consider: Parting it out if you have time and space will bring the most $ for what you have. You may want to remove the engine to swap into a different Previa if one should turn up. Craigslist is your best bet here.