I want to swap my Bolero to a Rcd510dab. It should be a straight swap, should I need to disconnect the battery first?

I wouldn't say so. I've removed my HU a couple of times to do various jobs and only ever disconnected the plugs on the unit.

As long as you don't go sticking screwdrivers into the various plugs I see no issues.

Thanks swapped without having to disconnect battery all fine!

Glad all was well

I would have said remove the radio fuse first, as I managed to arc the aerial amp to the bodywork once and nearly **** myself when it wouldn't switch on afterwards.

 

To my relief, it was just a blown fuse. So I never chance that again, especially with unpredictable and convoluted VAG electrics.