Having recently replaced my OEM pump, built the Walbro pump, installed AND un-installed the Walbro, and then installed a new OEM pump..... change your pump in your shop. It *could* be done on the side of the road.. but why? For one, the factory plastic fuel fitting are, at best, barely adequate. They may break when you remove them, they may already be broken (like mine were), or they may be fine. I doubt you will have spare fittings or the ability to mangle the vinyl fuel line to accept new fittings on the side of the road. Also the pump does not come out without some contorting - think Tetrus. Then even in the comfort of my shop I was worried about contaminants entering the tank. Cannot imagine what it would be like on the side of a windy road with a hole the size of a coffee can in your fuel tank. And I question whether the built spare pump would survive being carried as a spare. Once you see the entire contraption out of the tank you will understand what I mean.
For the Walbro retrofit - I got this kit intended for the WRX off Ebay that has the GSS342 pump and the bits you need (it was only $79 back early-pandemic!)
You can shop those parts numbers around for the best deal. My pump was legit Walbro with metal internals - and I checked out the Ebay seller before buying the parts.
