It's a wedge of money to sink into a car that will struggle with traction. This is why VAG uses Haldex or Torsen on the Golf R/performance Audi's.
To answer the OP - 330 Bhp, how hard is it? Not very. Why don't you get a remap first and see what you think if it's going to be a daily driver. For Santa Pod? Buy an Evo.
Reliability? Well it depends on what sort of life the engines had but on nearly 100k I would be expecting component failure as a possibility modded or not at some point.
Also as you have DSG, I wonder if uprated clutch packs would be necessary which would add to the upgrade costs.
