Here we go again...
The guy with a shop and a $27,000 roll away is telling the guy with neither, "it's easy".
Nobody will lend you tools or a shop.
The liability, your lack of knowledge and the chances you could could screw up, tie up the bay for weeks, waiting for an engine to get shipped, is the problem.
My advice: Pay the nice machine shop guy to fix your stuff.
If it breaks, he can fix it under warranty.
If you buy from an online store, you have no way to ship your core, (no way to rip it out if it has issues).
All the on line sellers have had lemons that missed quality check out.
If your mechanic or machinist screws up, they have to pull and replace the engine THEY BOUGHT.
If you buy the engine and it screws up, YOU pay to have it removed and re-installed.
Houston is a big place. Get a quote in writing from a reputable insured machine shop who also offers removal and installation.
Lot's of machinist's have shops they team up with, by the dozens.
Machine shops supply all over town. They know who's good, who's a hack, who is paying the bills, who's late and most importantly who could use a break and earn your business. Your machinist might find you an empty bay in 1/2 hour.
Make 1-2 calls instead of fifty.
"It's Easy".