I can confirm that the IP can be removed and reinstalled with the oil filter housing still in place. Sady and I did it when we put the new IP on his car. Wasn't even that hard to slip it into position. Now getting the bolts and nuts on is another story. Sady had a real good touch for getting the rear bracket on the pump.
Side note: we set his engine to 14 degrees ATDC and then put in the pump with the locking tool installed in it. Bolted everything down and removed the locking tool. Engine ran as smooth as any I ever heard.
I don't ever want to have to replace that gasket on the oil filter housing. if I have to, Sears is great for buying metric allen wrenches that you procede to cut up to whatever length you need. I've done that more than once.