Upgrading RCD300 --> RCD 310, few issues

[Qwertypants]

Apologies if this exact instance has already been spoken about and I've missed it somehow, but here goes.
My 2006 Golf mk5 is fitted with the stock RCD300 headunit. According to this thread (Upgrading 2nd generation radios (RCD 300, RCD 500) to 3rd generation (RCD 210, RCD 310, RNS 310, RNS 510, RCD 510) antenna adapter | my-gti.com) I don't need to upgrade my gateway and can just use the two fakra connectors, without having the power drain issue.
Can someone confirm that this will work, or if I will require a gateway upgrade (too many online sources are contradicting one another )
<Note: the owner of the RCD310 which i am buying, was using it in an '06 GTI without requiring gateway upgrade.>

Also, I was considering another idea. Since I bought my car (second hand) the unit overheats within 20 minutes, and after that I can't change songs or CDs without waiting for the unit to cool down and start working again. Is it possible that the previous owner already upgraded the gateway and was using a different headunit, hence there is too much power going in to the 2nd gen unit? It's a long shot but I figured It's worth to ask.

Any help would be appreciated.

[kamold]

I replaced the RCD300 in my wife's MkV (2007) and I DID replace the CANBUS gateway. I replaced it prior to upgrading to the RCD310 (have since replaced that with a Chinese 8' NAV unit) because my reading indicated that I would be susceptible to the battery drain issue.

Not sure about the overheating issue however it does sound possible...

[99_FGT]

No, the second issue is not as a result of the gateway, most likely a faulty unit or installation. The gateway "power drain" issues relates to the unit not going to "sleep" properly, and wanting to stay on (even if the screen was off with no sound coming out) and draining the battery.
Al..