No. At least not everything. Check their wiki link for details.
And pptp needs custom kernel too. Looks like OpenVPN is the only solution with stock kernel.

Custom kernel is not so dangerous. If you are afraid you can first load and boot custom kernel without touching the flash memory. You need linux flasher executable for this ('flasher -l -b -k kernelimage' boots is without flashing). And later when you find the kernel is working you can flash it without touching the rootfs. It can be done without loosing any data if done with care.