It's not fair to paint *every* tranny shop with the same brush, but having owned a business for 10 years located next to three different local & national tranny shops, it's a lousy business.
I wholeheartedly agree with ssmeee, check out angies list, or the BBB, at minimum. A business DOES NOT have to be a member of the BBB to have a file. Some shops will try to tell you that so you don't refer to their ranking.
As brief as possible...by and large...tranny shop MO's are to 'get a bite' on the job by you authorizing them to remove & inspect your tranny, then a barrage of successive phone calls drawing you in further & further with additional broken/non serviceable parts, then when you say STOP...
1) You nut up & pay the now $4,000 bill because "It's a great vehicle sir, but I've NEVER seen one this bad, it's just a fluke."
2) You pay them the man hours they've already logged, ($300-$600 even though ALL they've done is remove & disassemble, not reinstall as the book time states) throw all the (now completely disassembled) tranny in the back and tow your van home or somewhere else.
3) Decide the value of the vehicle isn't worth repairing & they offer you their time logged if you just sign over the title to them, so they can repair it & make a tidy profit. (Just look how many cars are perpetually for sale outside almost any tranny shop.)
Going with a national company & consider using their recommended installation facility gives you more leverage than an independent or chain shop.
Go to KBB.com & plug in your van's condition, see what trade in would be for one that is in good working order (keep in mind, 1% of all used vehicles qualify as Excellent condition, most are 'fair' some 'good'.)