Doubt you need a whole kit. Replace the 0-rings on the valve body. Grease them up before you reassemble the marker because they are easily torn during assemble. Even if they do not look bad...replace them. The 0-rings can be bought at hardware stores, I know Menards here in town carries them.
Here is a link to a disassembled marker;
If you want a regulator to hold up to CO2 then get a torpedo or a stabilizer. They are hands down two of the best regs for CO2.
Do not run a remote without a regulator on your rpm. You cannot use a remote and the bottom line reg on the marker b/c it will not regulate and you will get full tank pressure to your marker and really mess stuff up. The factory reg works off of the pin valve in your tank, so if your tank isn't on the reg (only your remote)...guess what the air isn't regulated at all. Either get the tanks anti-syphoned or a good regulator, prefer both and you won't have a problem.