I think that the new stem cost about £30 from a shop in the Netherlands and I got the open cockpit bars from someone on here for about the same. Installation was easy as the stem fits easily onto the headset in place of the tiller and the bars mount the same as any other stem mounted handlebars. Getting the brakes transferred required a bit of patience and finagling because, being hydraulic, I didn't want to change the cable length. It would have been slightly easier had they been a fraction longer. Bar end shifters are easy to install on nearly any bike and certainly no different here.
Difference? Getting started and climbing hills feels a lot more stable. I think mostly this is because bigger movements in the arms have less effect on the front wheel. Good when the front is a 20". Conversely, at higher speeds it felt a little less stable and that may be because you aren't able to brace your upper arms against your core. Moving away from trigger shifters on a tiller to bar ends on open cockpit meant that changing gear felt a lot easier as well as not causing the front wheel to twitch. This is all highly subjective and personal though. Other people will rightly find that tiller is better suited to them. Potentially I'd most prefer underseat but I'm not about to start retrofitting that.
