No need at the moment to consider replacing all, what you need is a replacement control rod for an 'old style Truma 5002' control rod,.asking for 'old style' being very important as the later one is completly different
The 3002's rod being a bit short, the 5002 is too long but can now be shortened at the control knob end to give the correct length, about 40mm from memory?.
The carver version used a short plastic and piano wire adaptor to connect rod to gas valve, it was/is common for these to fail, often leaving the broken brown plastic end in the top of the gas valve. This broken bit is usually very stiff to remove, however it does with care come out, leaving a hole to except the, designed for, Truma version's wire with a little bent loop or 'eye' on the end.
It must though be considered you have no idea of the history and it obviously has not been used for some time, it is then very important for your safety to get the fire checked out/serviced professionally before use.