To be honest I am surprised you got a year out of an MTB chain.
Of course it depends on conditions but I have seen some who have worn through a chain and cassette (and sometimes two pair of brake pads as well) over the course of one weekend. In these cases it is usually due to dusty conditions and an endurance race format, but these guys are not neccessarily soloists either, and they do know to relube regularly throughout the event.
In other words, chain wear like that is not uncommon or premature (I would even go so far as to say it is probably better than average).
There is nothing wrong with thoroughly cleaing the chain as long as the lube you have washed out is replaced. Kerosene is my favourite solvent for this
I'm not in favour of dry lubes like pro link as they have never removed the noise aspect of a dry chain, and they have never prevented the ingress of dirt under the rollers (where the wear takes place). Dry lubes also possess no physical property to keep them in place under the roller. A dry lube is, of course, a (dry) solid which can be pushed around by the roller but will not necessarily pull itself back into places where it was pushed out of.
My preference has always been for a wet lube (preferably a viscous one - 3in1 is a pretty good example of a general purpose wet lube). Being a viscous liquid, it has significant surface tension wich helps to trap it under the rollers, filling in the gaps where dust may ordinarily get in easily. Note that this doesn't prevent the ingress of dust, but significantly slows it down. Eventually, no matter what lube you use, dirt will get in and re-lubriation is necessary to flush the dirty lube out, or a degrease and relube may be called for.
The issue with collecting dirt on the outside is largely a cosmetic one. At least you know that once a dust particle is stuck to the outside of the chain, it isn't going to get up by itself and walk in under the rollers. Nevertheless dirt on the outside is unsightly and I always use a rag dampened with some solvent to wipe the excess lube off. Wiping down regularly (even when not lubing) helps with this.
If you prefer dry lube, use it by all means but it never has lasted as long or provided the quiet operation you get when wet lube is applied properly.
And yes you are getting carried away on replacing components...
I gather you need to change the chainset becasue the chainrings are riveted to the crank and cannot be replaced individually. The cheapest and technically easiest option for now would be to replace it with another FC-M191. It is true that, in the long run, it might be cheaper to have a crank with removable chainrings, but the up-front cost is probably equivalent to a couple of the FC-M191 anyway. You may also run into difficulties getting hold of replacement 8 speed chainrings.
When looking at quotes for service charges, always bear in mind what the whole bike cost you. Upgrades to fancier cranks could end up costing you a good proportion of the replacement cost of the whole bike. If you are about to spend more than half of the replacement cost of the bike, then think very carefully. I'm not saying you should think about buying another bike, but you should, at least, think about sticking with components which are in keeping with its original worth.
At this level you do not need to concern yourself with chainlines since this has next to no effect on wear. To extend the life of your componenets, think more about regular lubrication, reducing crosschaining (running small chainring to small sprocket or large chainring to large sprocket) to a minimum, and try to use the full range of gears available (ie spread the wear out over more chainrings/sprockets).
