Hey Jossef, welcome back. Usually the Tx/Rx is already bound from the factory. However, if you power it all up and nothing works....then you know what you have to do.
What you probably
will have to do is calibrate the throttle and ESC. This is a procedure listed in your manual. This will set the ESC's throttle range to match the radio's throttle trigger range. It's important to do. It usually goes something like this: With the radio on, press a SET button on the ESC then power up the ESC. The ESC beeps a few times. With the throttle trigger at neutral, press the SET button. ESC beeps once. Pull full throttle on the trigger, press the SET button again, ESC beeps twice. Give the throttle full reverse, press SET button, ESC beeps three times. Done. Turn off ESC and turn it back on again, you're ready to go.
As for Lipos, there are many places you can order them from. I've been using Gens Ace Lipos I get from HobbyPartz.com. Good packs, decent price. I also started using SMC Lipos. Also excellent packs and even better prices. However, they seem to be low on stock right now, probably due to the dock worker's strike.
Your 7.2V 3000mah pack is probably a 6-cell NiMh pack. NiMhs are fine for your brushed motor system. 3000mah will probably get you 10-15min run times. And I think I remember the Raider was pretty quick with a 6-cell NiMh. If you wanted more speed, you could go to a 7-cell NiMh, providing the battery compartment can fit one. 7-cell packs come in "stick" and "hump" packs. The "stick" pack has all seven cells in a flat arrangement. The "hump" pack has the 7th cell stuck on top of the pack in a hump, so the pack length is the same as the 6-cell, but it has that hump on top, which can interfere with some battery retention straps.
Back to Lipos: if you want to go Lipo, you'll probably stick with what are refered to as "2S" packs. This refers to the number of 3.7V Lipo cells the pack has. 2S = 7.4V. Like NiMhs, Lipos are rated with a number that represents the pack's capacity, that's the "3000mah". Or 3000 milli-amp-hours. That's kinda small actually. You'd be much happier with 5000mah packs. They are a common size. We're now starting to find 6500mah and 7200mah packs that will also fit battery trays that fit 2S packs. Even a couple 10,000mah 2S packs, but they're thicker than most 2S packs and may not fit some cars.
You may notice Lipos have another rating: the "C-rating". i.e. 30C, 40C, 60C This rating is an indication of how much current the pack can supply in a given time. A Lipo with a 60C rating will have a higher output current potential than a pack rated at 30C. Not a big deal if you're running a brushed motor, or small brushless motor. But a big brushless motor system will pull LOTS of amps, so a higher C lipo would be required. The C rating has almost as large an effect on the price as the capacity, so don't over-buy. The brushed system in your Raider will do fine on a 25C-rated Lipo.
If you buy Lipo, you're going to NEED to buy a Lipo charger. DO NOT charge a Lipo on any other kind of charger, or you will have a fire, and I don't imagine you want to burn your house down.
This is a great little charger. for about $55. Quiet, and does the job. NOTE: Lipos require a little extra attention, in that, you do not want to leave them charged or discharged for long. They have a "resting voltage" they "like to be at". This is the Storage Voltage. And the charger has a Storage function. USE IT. When you're done for the day, put the pack on the charger, select "Storage" and hit start. The charger will charge the pack to about 3.80V per cell. Not doing this every time will shorten the pack's useful life, and, decrease its capacity (shortened run times).
I don't know what kind of battery connectors the Raider has, but if they're the old-school white Molex "Tamiya style" connectors, DUMP 'EM, NOW! Pick a connector: Traxxas, Deans, EC3, bullets....any of those are meant for high current applications. Those Molex things should be banned from the hobby.
Also, be aware that in buying these things, you're not guaranteed that the connectors will match. Gens Ace Lipos come with 5mm bullets. I picked Traxxas connectors a long time ago, so I have to cut off the bullets and solder on the Traxxas. But now, SMC has Lipos you can get WITH Traxxas connecotrs, or Deans, your choice! The two Lipo brands I mention usually for for less than $40ea for a 5000mah 40C pack. Better price than other brands like Traxxas, Venom, or Turnigy. SMC had some killer prices until they ran out of stock. But I got a couple 7200mah 60C 2S packs for $48ea.
Hope that helps ya.