I'm fairly new to the mod scene myself. If I can change my springs myself you can change a fuel pump, it doesn't look that hard, just a little smelly and messy. It'll be easy.

As for the VF34 it only kicks in a few hundred rpm later than a TD04, it's the least laggy thing you'll find. However I'm on a stock TD04 with TBE and Ecutek Tune and I'm happy with the results. Although if my TD04 ever dies I'll prolly get a new VF43.

The initial tune is costly but subsequent tunes are rather reasonable, I suggest stick in your process west, turbo and get a tune, then go from there. It doesn't need to be done all at once.