The UltraFlow is a high head pump so priming is probably as good as it gets with this pump. You can either replace the entire pump or just the motor. It usually makes more sense to just replace the motor if the wet end is in good condition and you don't need to change any plumbing. But since you have to change the plumbing anyway, it may make more sense to replace the entire pump. Either way is fine, it is basically an economic decision.

However, when looking at a replacement, you need to focus on max head because that is the only thing you can go on for priming ability. The higher the pump head, the larger the impeller and more effective the pump will be at priming. However, in most pump lines, the max head is the same for the various HP ratings so you can lower the HP to save some on electricity costs.

If you want to stick with Pentair, the Whisperflo is a good pump line but for priming reasons, I wouldn't go below 1 HP (full rated). So either the WFDS-4 or the WFDS-26 would be a good choice.

BTW, where is your location and how much do you pay for electricity? A VS may or may not be a good solution for you.