I've got an old Mossberg 22 RF model 152K that I've had since I was a teenager. Got it used from an Uncle that I did some work for in exchange for the rifle. The barrel is in poor shape probably from cleaning and I don't know when it got ringed inside. Still shoots but I have a new-old barrel I'd like to install. Threaded barrel onto a round style receiver. Just wondering if I'll have any trouble getting it apart and if anyone has any tips or links on removing the old barrel or installing the new one?

First step is to apply a good slug of Kroil all around the barrel-receiver joint and let it soak a day or two.
This will penetrate and dissolve any old grease.  
Heat is not needed and may actually cause problems.  The Kroil does the same thing as heating.
If you do use heat, WARM the joint, don't heat it up so hot you might cause damage.
Hot enough that you can't keep your hand on it for more then a few seconds is plenty hot enough.

Soak with the Kroil 12 hours or so, then use a plastic hammer or a plastic screwdriver handle to give the receiver a few sharp raps all around.  The vibrations will help loosen the barrel and help the Kroil to penetrate faster.
Let soak a day or so after rapping the receiver.

Use a real gunsmiths barrel vise and a real gunsmiths receiver wrench.
An expedient barrel vise can be made from two blocks of HARD wood like oak.  
Rout a groove in each block slightly larger then the barrel, then use epoxy to mold the blocks to the barrel.  
Do one block at a time and mark them as to which side they go on and which end goes toward the muzzle.
A good release agent is Johnson's Paste Wax, available at most hardware stores.
You can use hardware store one hour epoxy or buy epoxy bedding from Brownell's.
Most stores are now selling only 5 minute epoxy, don't use that.

What  you want is when you clamp the blocks tightly on the barrel you have a slight gap between the blocks.

Clean the inside of the blocks thoroughly with alcohol or paint thinner to remove any release agent or oils, (no Acetone or lacquer thinner).

Clean the outside of the barrel thoroughly to remove all dirt or grease.

A LARGE shop vise might be enough to hold the barrel since most .22 barrels weren't installed that tight.
BUT... if the barrel is tight a shop vise won't do it, the barrel will just turn in the blocks no matter how tight you tighten the vise.
A good barrel vise for a lower price is the type that bolts to a HEAVY shop table or a truck bumper.  
Many shooters who have switch barrel rifles mount the barrel vise to the bumper so they can change barrels right there on the range.

http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/vises-accessories/barrel-vises/barrel-vise-prod58959.aspx

For the receiver you'll need a receiver wrench since making wood blocks as above usually just won't work on a receiver because there's no good way to mount the blocks in a extended handle to turn the receiver without it slipping in the blocks.
Again, degrease the receiver thoroughly.

Again, Brownell's sell gunsmiths action wrenches:

http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/wrenches/action-wrenches-components/action-wrench-prod16140.aspx

http://www.brownells.com/gunsmith-tools-supplies/general-gunsmith-tools/wrenches/action-wrenches-components/universal-rifle-action-wrench-head-prod25117.aspx

When installing the new barrel use an anti-seize compound on the threads.
A .22 barrel doesn't have to be real tight, but it does need to be tight enough there's no way it will vibrate loose over time.

Be careful what tooling you use, since expedient barreling tools can easily damage things.  As example, the wrong tooling can crush a .22 receiver if you have to tighten it too much.  Good actual gunsmithing tools won't do damage as long as you use them properly.

Good luck.

Great information and thanks for your time. I'll start on my project before long.  Don't want to do any damage as this rifle has sentimental value and I want to make it as close to new as possible.

I agree.  That's some damn handy info.  Printed this page and will keep in my gun notes.

I had barrel liner installed in my dad's Win 1906. No barrel removal and shoots great. Thinking about having it done to my Marlin 27S in 25 WCF.