How hard it is to replace the rca input on the shindo amplifier?

I’m glad that actually you chose the path of learning instead of hiring someone for insubstantial problem. I know many today’s audiophiles even refuse to learn to work on elementary items, but not this time indeed. The phrase on each today’s electronic component "Only for qualified technician" appeared in 90’s operation manuals instead of detailed schematics and service manuals to keep you away from learning and keep you closer to spending indeed. WES51 is very good investment for all electronic repair needs. I use one since 2002 SAME model. That tells about the undisputed quality of a tool.
Now next step you’ll be shopping for de-soldering tool I guess.

Any reccomendation on De-soldering device?

I use the electric one with sucker bulb and found it the most useful for all applications
I would probably want to use electric one with button, but 30W is insufficient most of times.
https://www.parts-express.com/cat/desoldering-tools/520

For many years I've had one of those spring loaded solder vacuuming devises ("solder sucker") where you just point it at the solder and hit the button…instantly sucks up the hot solder no problemo, weird but effective.

Desoldering stations are actually a lot more expensive then soldering irons.  Used Hakko or Pace desoldering stations are $250-300 used on ebay.  I bought my Hakko 472B years ago for about the same price.  Used pricing hasn't really changed in 10 years.  Cheapest recommended new item is Hakko FR-300 for about $270 (it has the pump built into the self-contained handle -- not as good as a full desoldering stations like the used 472B).  If you look at a used station, make sure it includes a vacuum pump (some stations require external "shop air" for suction).  Otherwise, you're looking at the cheap options that czarivey has mentioned.