Currently I have 3 chainrings on my 8 speed drivetrain, 42/32/22.
Im changing my entire drivetrain to 9 speed i.e. cassette, chain and chainrings. For training purposes what I would like to do is only keep the middle ring which is the 32, get rid of the smallest ring and substitute the largest ring with a bashguard. Can I do that? Will I have spacing issues if I use only one ring (32t) and a bashguard with a 9 speed cassette?

Heres the ring and guard that I was going to use:

Blackspire Ring

RaceFace Bash Guard

You wont have spacing issues but you may need a guard on the inside as well to not loose the chain.

Of you could just leave the mech on and use the limit screws to hold it in the correct position over the remaining ring.

If you are just riding on the road you can probably get away without but it is not nice when the chain falls off at the wrong time.

you can also keep your front derailleur on there to act as a chain guide. or just use half of it, to prevent it from dumping the chain to the inside. you may want to post something in the cyclocross forum, as that is a very common setup for cx.

Is it worth spending the extra $ on an e13 guide or will the front der be suffice?

I raced cross for two seasons with the FD method and it works flawlessly. Don't be tempted to get a third eye chain watcher. I've heard some pretty bad things about them. Google it if you don't know what I mean...

Currently I am using the ground down cahin ring bash guard and a half deraillure. The bash guard of course will protect your chain ring

the front derailuer method is a cheap replacement for an e13 guide, it doesnt function as quite as well... but hell your saving $130 bucks (or how ever much they are) it works fine, and with the bash gaurd (also a good chose) it will work welll