Being a student, and thus perpetually broke, I am one of the cheapest guys you're likely to meet. And even I pay others to do my brake/fuel line work. It's just not worth the hassle...
As for the proportion valve, I'm pretty sure the l4 setup is similar to my V6, and it's against the firewall, right above the steering rack.
Good luck, I don't envy you the job ahead.
P.S.: I see you're in Wisconsin...salt-belt country not far from me. No wonder your lines are rotted.
__________________

1990 5spd V6 Camry (Still kicking at 393,000km) 1991 Celica GTS -- Pappa needs a 3SGTE...and AWD for all this friggin' snow
Honda my A$$, you just can't kill a Yota...