Bike noob here, I have a pretty old Suntour Fleetwing with step-over steel frame which I bought used/refurbished/multiple parts replaced from a reputable shop last week. Its 5 speeds with a single stem shift which I am finding really bothersome. Is it possible to make it to a thumb shifter instead? Id really rather not have to look down and remove my hand from the handle while driving. How much could I expect to pay for such a conversion?

Ravenology:

Your post seems to contain a typo, as it is asking whether you can convert the thumb shifter to a thumb shifter. I'm assuming, based on the post's title, that you have a stem shifter, and want a thumb shifter? I bought these things on niagaracycle.com for $8/pair, and they kind of rule. got 'em on my 3x9 Long Haul Trucker....

https://www.niagaracycle.com/product_...oducts_id=5146

they have just the right (rear) available ala carte for $5:

https://www.niagaracycle.com/product_...ucts_id=418238

These creatures sort of ratchet; they run as friction shifters, but they "click-click-click-click",although the clicks are non-indexed and don't correspond to any particular gear. Pretty nice piece of metal and plastic, for the money. (Came with cable/housing,too.)

hth
-rob

I meant stem shift. Whoops. Its hard to push up and down, and I have to take my hand off the bar, so its al ittle distracting when Im in traffic

What kind of handlebars do you have? Thumb, trigger, and grip shifters (made for mountain bikes) will not be the correct clamp diameter for most drop bars.

Im not sure what they're called, but this is basically my bike except mine has a step-over top bar:
(Haha, I even have a basket and clip for my U-lock, cept mine's flaked dark green)

I'd go with the shifters posted by surreal. I'm 95% sure they'll work with your handlebars. This should be an easy, inexpensive swap. Those shifters even include cables and housing.

Is it something I could do myself at home, or would I need a bike shop to do it? I have 0% experience with bikes save for when I was 10 and riding up and down my parents driveway.

You should be able to do this yourself. You will need basic hand tools, side cutters, and Allen wrenches. Before you attempt it, check out Sheldon's articles on cables and derailer adjustment:

https://sheldonbrown.com/cables.html
https://www.sheldonbrown.com/derailer-adjustment.html

Note that you don't have indexed shifting, which makes things a lot easier to setup. You just need to remove the old cables and shifters, and replace with the new shifters and cables. Unless things are working poorly now you don't need to make any actual derailer adjustments.

Great! I think Ill check out the cost of having it done at the shop, unless its very expensive I think Id like to play it on the safe side. I have the tools and patience, just not sure if I wanna trust myself on something Ill be riding around

ok, but you can do this easy witha a few tools you oughta have anyway. a greatt project to introduce a noob to the joys of self-wrenching

-rob

Stem to thumb, both ratchet/friction , no problem.

I had an older bike with stem shifters, and the rear derailleur had a solid cable going to it that actually pushed / pulled the derailleur. I had to replace that with a more modern spring loaded one to convert to thumb shifters.

Looks like its pissing rain, so I think Ill just head down to the shop without my bike and see how much the kit costs. I'm too scared to take it out in the rain now that Ive gotten all the rust off, haha.

I really hope I don't have to replace mine, its original to the bike and quite ornately beautiful now that Ive got it polished up.

Great, got a kit for a shimano shifter. it clicks and has numbers to corresponding gears! Exactly what I wanted. Hopefully I can figure this out and wont end up with a fixie stuck in 5th lol.

5 speed indexed? really?

Great, I messed up. I must have threaded the derailleur wrong...its just stuck in 5th now...bummer. Guess Ill have ot walk it over in the rain tomorrow. Poor thing

I've seen it

I put together the derailleur exactly as it was before, yet still no shifty. =[

pics, please. let's see this derailer.