Chainsaw Repair

I have used friends chainsaws for years and have a small home owners model stihl 170, but finally needed my own saw and after looking around my friend had a used MS-290 farmboss with a scored cyl.  The saw ran ok but failed the pull chain compression test and since I got the saw for 60$ I decided to do a rebuild on it.  I am quite mechanically inclined but never on 2-stroke stuff so this is a new venture for me. 

I ordered a used but good stihl 029 cylinder and piston for 75$ off eBay, got new OEM crank seals, oem impulse tube and fuel line, oem muffler and got a new set of caber piston rings.  My friend works as the mechanic at a stihl dealer and has done many cyl swaps so he is going to help walk me through it.

Questions I have are since I have the thing apart I would like to replace the crank bearings but don't wanna pay 50$ for oem ones.  Are there any good aftermarket ones that are cheaper?  I see a lot on eBay that are cheap but don't wanna put all the money into the saw only to have it ruined by junk bearings.  Are the eBay ones junk or do they last?

I read about tuning the saw and my friend does it by ear but I bought a 16 dollar tach on amazon to try to get it tuned perfectly.  Where can I find the correct rpm for the saw with a 20inch bar?

Also I would like to do a muffler mod but once again don't want to risk hurting the saw after I put money into it.  Is there any negative effects to the MM and is it worth it?  Would love advice on doing it on my 290 if anyone has any. 

And lastly, will the MM change the rpm I should tune the saw to?

Thanks a TON and if anyone has any resources I should look into I would greatly appreciate anything

029 is smaller bore then 029 super / MS290

Muffler mod on 290 takes about 30mins. Seen as much as 23% quicker cuts with MM and carb retune.  Pics in other stihl 290 310 390 threads

Read on Tachs  http://chainsawrepair.createaforum.com/ported-saws/chainsaw-tachometer-choices/

Got the cyl today and it looks great, the piston measures 45.89 mm is that the smaller or the larger bore?

I have been looking around the site but haven't found a specific thread for a MM on the 290

The tach I got is a tiny tach cst with a .5 second refresh rate

Thanks guys any info you can provide helps me greatly!!

Good on the tach.

mm  http://chainsawrepair.createaforum.com/stihl/stihl-ms390/msg3208/#msg3208

mm bolts  http://chainsawrepair.createaforum.com/stihl/muffler-bolts-290-310-390-250-etc/msg8446/#msg8446

stihl 029 45mm bore 54.1cc

stihl 029 super ms290  46mm bore  56.5cc

Measure your piston front to back at the bottom of the skirt.
I wouldn't tune over 13000 RPM.
Look for C3 rated bearings.
That's one of the ways to open the muffler. Cut the deflector back to the first bend.
Pull the carb limiters and tune appropriately. ( I seem to add about 1/2 turn on the H )
Have fun!

Never mind the photos are too big I guess