Novice opening up vivitar 200mm 3.5 for fungus removal?

In a free bag of Pentax M42 stuff, I got a Vivitar 200mm 3.5 telephoto lens with some internal fungus.

Novice that I am, what are the chances I take the lens apart and put it back together?
No dedicated tools to speak of.

The fungus looks minor (to me) and I am giving it a bit of sun exposure every day.
I may be better off leaving it as is and enjoy it as casual use?

You need a lens spanner https://www.ebay.com/itm/DSLR-Lens-...333810?hash=item2f3ab3eff2:g:v~cAAOSwH8Vd7Fr1 to remove the element retaining ring paying attention to 1). how many turns a retainer has to be turned to remove it, 2) the orientation of the element, 3). the number of shims and whether they are if front of the element or behind the element or in the case of both the number and thickness of the shims on each side.
Retainer rings are usually sealed with thread locker that dissolves with acetone. Apply the acetone with a cotton swab, liberally, and allow to soak in for 3 to 5 minutes.
Lens cells should be removable without disassembling the lens barrel or aperture ring but the mount ring may need to be removed.

I’d estimate you have 0% chance of the adventure ending with a cleaned fully operational lens. (Just being truthful )

My goodness, what a negative nancy. Free lens, what's the loss?
Many long lenses are much simpler than telephotos. Removing the front group
or element should be a matter of removing the decorator ring and maybe a retaining ring behind it.

If it were a zoom, I would say no. But, a simple prime; go for it!

I suggest you visit Richard Haw's excellent site and read up on his lens repair fundamentals.

https://richardhaw.com/lens-camera-repair-fundamentals/

Richard deals almost exclusively with Nikon products, but the basics are the same.