you could try to fix it yourself. Find a good toyota Mechanic. A lot of them do side jobs, stop by on a Saturday after 2pm and some of the Mechanics might offer to do the jobs the following week.
Most of the leaks can be solved in your driveway. You've gotta search through this forum and Club Lexus. You should find easy ways to handle the Valve gasket, distributor O ring, radiator replacement, and the trunk latch. The trunk is held up by two shocks like the Front hood is. PepBoys, NAPA and the Toyota Dealer should have Truck stuts. Radiator replacement, valve gasket and distributor ORing same place sources. They are relatively cheap to buy there; it's the labour that racks up the bill.
Gauge Cluster you can send it out to Mikado Industries in San Francisco. Search the LS400 Forum, I've placed the address there. It's about $2-300 to replace all the bulbs and cleaning out the connectors.
Th Rear engine seal, you'll probably need access to a lift. save that for the dealer or AAMCO
The Spiral Cord for the Airbag, I'd buy that new from the dealer as well.
Now here's the bad news; anything related to the engine and transmission will end up costing you more money to fix because there's a reason why the leaks happened in the first place. The last owner or you didn't maintain the engine and transmission like it's supposed to be.
Here's an example; with your Radiator being busted; since i don't know what caused it I'm thinking your water pump, thermostat, rubber hoses and a number of seals need to be replaced.
This is why I was saying find a cheap Toyota Mechanic who is willing to fix all your major leaks for $5-600. Most if not all will be labour $$$. You maybe able to have him/her replace the Trunk Struts, and the Spiral cord for free. I've never replaced the spiral cord myself so I can't say about how he'll charge you, but if it's not easy to get to they'll try to charge you. If you can get them all done at the same time. Most of them work quickly if they don't have to search for new parts.
Good luck and keep asking questions