Will a 1998 saturn engine parts fit an 1995 saturn engine

Call around to your local auto parts stores, most likely one of them will read your code for free and tell you what needs to be fixed if anything. (They're in the business of selling parts, so they're hoping the check engine can be fixed by a part that you can buy from them and replace.)

Pep Boys, AutoZone, O'reilly, Advance Auto and Napa Auto have been known to read your codes for free.

No, timing is not like that any more. Timing lights are almost obsolite. Your computer takes care of all of that now. Disconnect your battery for a few minutes and connect it again, this will reset your engine timing

What is the engine size?

yes.

No, you need a 96 through 98 engine, make sure the one you get is the same as yours, that is if you have an SL1 your donor car must be an SL1, SW1 or SC1 and if you have an SL2 then your donor car must be an SL2, an SW2, or an SC2. You can buy rebuilt engines for about 2000 with core exchange
might make more sense if you intend to keep it a while and if a manual then do the clutch while it is out.

same part should fit 96-99, call around to local junkyards. there are also some scavengers selling old saturn parts on ebay, contact one through an ad and put in a special order. usually a few old saturns being sold for parts on craigslist.

the SL seats were pretty interchangeable, so i would imagine the SC seats are as well. there are only 4 bolts so it does not take long to check/

It's a 4 cylinder, engine size 1.9L SOHC.
Napa oil filter number 21348.

There are two engine mounts, one on each end of the engine, called "dog bones" as they are shaped like bones. You can buy them new at any parts store or on ebay. Same parts fit most all saturn 1.9L 4 cylinder cars from 92-99 which all have the same basic engine. There is also another mount on the top of the engine to the left, and one on the bottom right side under the transmission. The dog bones can be replaced easily, but the other two require some thought as the engine must be supported and lifted independent of the car.

Good question, the answer is "yes", "no", and "maybe". GM shares a lot of parts internationaly with Opel, Saturn, GM, Chevy, Pontiac, etc. Especialy engine parts. Chassis and body is a different story. You may find tie rods, struts, etc the same, but a headlight won't fit from one to the other. If you've got a 2004 Saturn Ion, you likely have a 2.2 EcoTec. Pretty much all EcoTec parts will fit in one form or another, from one to another. Alternators, starters, etc. You may need to swap plug locations or types, but the actual hard part should "fit". You would need to go dumpster diving to compare or contrast. I guess it all depends on what you need? the Stick