Your first step should be to connect an R134a manifold and see if the system has any pressure. HF sells a manifold for around $60, although I would recommend a mastercool 66661 ($75 on amazon).
If no pressure in the system - then you may have punctured the condenser in the collision. If this is the case you will need a new condenser AND a new receiver drier (the drier contains desiccant, and if the system is open it will have absorbed moisture). I have had good luck with a Denso 477-0518 condenser (~$60) and Denso 478-0500 drier (~$15) on my rig. You may also need to pick up an A/C O-ring set at your local auto parts store for a few bucks, because I dont believe the drier/condenser comes with all the ones you need.
Whenever you replace a component of the A/C system, oil must be added! The service manual will tell you how much oil for which components. I believe 20cc's is required for receiver drier and 45cc's for condenser. The oil you need is PAG 46 (a bottle of Johnsen's is about $10 on amazon). Personally, I used a syringe to deliver the oil into the drier, but it can be done several ways. Installation of the replacement parts is fairly easy - I only had to remove the grill.
Now you need vacuum down the system with a vacuum pump. Again, HF sells a few in the $100 range. I have had good luck with a Robinair 15310 ($110 on amazon). I wont go into the specifics on the entire process, since you can find it on youtube, but basically you will open the valves, pull it down under vacuum for about 30 min, then close the valves and shut of the pump. Make note of the vacuum and let it sit for 30 minutes to verify the reading does not change (no leaks). The max vacuum you can attain is dependent on your elevation (you will most likely be in the 24-27 in HG range).
You will need a puncture valve for the R134a can (Mastercool 85510, $12 on amazon) and a couple cans of refrigerant (Johnsen's 6312, $10ea on amazon).
Now you basically disconnect the line to the vac pump, and connect to the puncture valve (puncture valve installed on refrigerant can). Puncture the can with the valve, and then you will want to purge that line (loosen it at the manifold for a second). I believe the spec is 21.2oz to 24.6oz of refrigerant for the system. You can keep an eye on how much you are charging by simply placing the can on a scale. From here you follow the charging process. Be sure to charge the LOW side (See youtube for process, but basically its: start engine, A/C on, fan on, outside air, and run it until the the compressor has pulled in the appropriate amount of refrigerant).
When charging is complete, you can also verify your nominal running pressures at high/low side are good (see manual for specs).
Some random pics I found in my archive:
