It's only a couple of hundred to have them cleaned, you'd be looking at at least that anyway for used injectors in unknown condition instead of having a set refurbed to new condition.
The 34 has a shorter wheelbase so it's a bit nimbler. Weight wise they're both pretty similar, chassis wise they're both pretty similar too, same front and rear ends.. same car really apart from the body panels and the wheeelbase.
Yeah a PayPal dispute usually gets you a full refund. You and a seller both get a chance to plead your case and then PayPal make their decision based on the evidence. It could go either way but generally they'll side with the buyer
Yep you gotta remove the crank. Requires the snout of the crank to be machined down then the collar heated and slipped onto the end, then as it cools it shrinks onto the crank.